Utilizing correlations between PPG signals and iPPG signals to improve detection of physiological responses

ABSTRACT

Disclosed herein are systems and methods for detecting a physiological response using different types of photoplethysmography sensors. Examples of physiological responses that may be detected include an allergic reaction, a stroke, a migraine, stress, certain emotional responses, manifestation of pain, and blood pressure. In one embodiment, a head-mounted contact photoplethysmography device measures a signal indicative of photoplethysmogram signal at a first region that includes exposed skin on a user&#39;s head (PPG signal). A camera, located more than 10 mm away from the user&#39;s head, captures images of a second region that includes exposed skin on the user&#39;s head. A computer detects the physiological response based on: (i) imaging photoplethysmogram signals (iPPG signals) recognizable in the images, and (ii) correlations between the PPG signal and the iPPG signals.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 62/874,430, filed Jul. 15, 2019, and U.S. Provisional Patent Application No. 62/928,726, filed Oct. 31, 2019.

This application is a Continuation-In-Part of U.S. Ser. No. 16/156,586, filed Oct. 10, 2018, that is a Continuation-In-Part of U.S. application Ser. No. 15/832,815, filed Dec. 6, 2017, which claims priority to U.S. Provisional Patent Application No. 62/456,105, filed Feb. 7, 2017, and U.S. Provisional Patent Application No. 62/480,496, filed Apr. 2, 2017, and U.S. Provisional Patent Application No. 62/566,572, filed Oct. 2, 2017. U.S. Ser. No. 16/156,586 is also a Continuation-In-Part of U.S. application Ser. No. 15/859,772 Jan. 2, 2018, now U.S. Pat. No. 10,159,411.

This application is a Continuation-In-Part of U.S. application Ser. No. 16/453,993, filed Jun. 26, 2019. U.S. Ser. No. 16/453,993 is a Continuation-In-Part of U.S. application Ser. No. 16/375,841, filed Apr. 4, 2019. U.S. Ser. No. 16/375,841 is a Continuation-In-Part of U.S. application Ser. No. 16/156,493, filed Oct. 10, 2018. U.S. Ser. No. 16/156,493, is a Continuation-In-Part of U.S. application Ser. No. 15/635,178, filed Jun. 27, 2017, now U.S. Pat. No. 10,136,856, which claims priority to U.S. Provisional Patent Application No. 62/354,833, filed Jun. 27, 2016, and U.S. Provisional Patent Application No. 62/372,063, filed Aug. 8, 2016.

U.S. Ser. No. 16/156,493 is also a Continuation-In-Part of U.S. application Ser. No. 15/231,276, filed Aug. 8, 2016, which claims priority to U.S. Provisional Patent Application No. 62/202,808, filed Aug. 8, 2015, and U.S. Provisional Patent Application No. 62/236,868, filed Oct. 3, 2015.

U.S. Ser. No. 16/156,493 is also a Continuation-In-Part of U.S. application Ser. No. 15/832,855, filed Dec. 6, 2017, now U.S. Pat. No. 10,130,308, which claims priority to U.S. Provisional Patent Application No. 62/456,105, filed Feb. 7, 2017, and U.S. Provisional Patent Application No. 62/480,496, filed Apr. 2, 2017, and U.S. Provisional Patent Application No. 62/566,572, filed Oct. 2, 2017. U.S. Ser. No. 15/832,855 is a Continuation-In-Part of U.S. application Ser. No. 15/182,592, filed Jun. 14, 2016, now U.S. Pat. No. 10,165,949, a Continuation-In-Part of U.S. application Ser. No. 15/231,276, filed Aug. 8, 2016, a Continuation-In-Part of U.S. application Ser. No. 15/284,528, filed Oct. 3, 2016, now U.S. Pat. No. 10,113,913, a Continuation-In-Part of U.S. application Ser. No. 15/635,178, filed Jun. 27, 2017, now U.S. Pat. No. 10,136,856, and a Continuation-In-Part of U.S. application Ser. No. 15/722,434, filed Oct. 2, 2017.

U.S. Ser. No. 15/832,855 is a Continuation-In-Part of U.S. application Ser. No. 15/182,566, filed Jun. 14, 2016, now U.S. Pat. No. 9,867,546, which claims priority to U.S. Provisional Patent Application No. 62/175,319, filed Jun. 14, 2015, and U.S. Provisional Patent Application No. 62/202,808, filed Aug. 8, 2015.

U.S. Ser. No. 15/182,592 claims priority to U.S. Provisional Patent Application No. 62/175,319, filed Jun. 14, 2015, and U.S. Provisional Patent Application No. 62/202,808, filed Aug. 8, 2015.

U.S. Ser. No. 15/284,528 claims priority to U.S. Provisional Patent Application No. 62/236,868, filed Oct. 3, 2015, and U.S. Provisional Patent Application No. 62/354,833, filed Jun. 27, 2016, and U.S. Provisional Patent Application No. 62/372,063, filed Aug. 8, 2016.

U.S. Ser. No. 16/156,493 is also a Continuation-In-Part of U.S. application Ser. No. 15/833,115, filed Dec. 6, 2017, now U.S. Pat. No. 10,130,261. U.S. Ser. No. 15/833,115 is a Continuation-In-Part of U.S. application Ser. No. 15/182,592, a Continuation-In-Part of U.S. application Ser. No. 15/231,276, filed Aug. 8, 2016, a Continuation-In-Part of U.S. application Ser. No. 15/284,528, a Continuation-In-Part of U.S. application Ser. No. 15/635,178, and a Continuation-In-Part of U.S. application Ser. No. 15/722,434, filed Oct. 2, 2017.

U.S. Ser. No. 16/453,993 is also a Continuation-In-Part of U.S. application Ser. No. 16/147,695, filed Sep. 29, 2018. U.S. Ser. No. 16/147,695 is a Continuation of U.S. application Ser. No. 15/182,592, filed Jun. 14, 2016, which claims priority to U.S. Provisional Patent Application No. 62/175,319, filed Jun. 14, 2015, and U.S. Provisional Patent Application No. 62/202,808, filed Aug. 8, 2015.

ACKNOWLEDGMENTS

Gil Thieberger would like to thank his holy and beloved teacher, Lama Dvora-hla, for her extraordinary teachings and manifestation of wisdom, love, compassion and morality, and for her endless efforts, support, and skills in guiding him and others on their paths to freedom and ultimate happiness. Gil would also like to thank his beloved parents for raising him with love and care.

BACKGROUND

A photoplethysmogram signal (PPG signal) is an optically obtained plethysmogram that is indicative of blood volume changes in the microvascular bed of tissue. A PPG signal is often obtained by using a pulse oximeter, which illuminates the skin and measures changes in light absorption. Another possibility for obtaining the PPG signal is using an imaging photoplethysmography (iPPG) device. As opposed to typical PPG devices, which usually come in contact with the skin, iPPG does not require contact with the skin and is obtained by a non-contact sensor, such as a video camera. iPPG has emerged as a promising technology for detecting physiological signals and various physiological responses whose manifestation involves changes to facial blood flow (e.g., an allergic reaction, a stroke, a migraine, stress, certain emotional responses, manifestation of pain, and blood pressure pulse waves). However, due to the fact that iPPG signals are typically acquired using non-contact cameras, the iPPG signals are often noisy and greatly affected by confounding factors such as illumination from the environment and body movement. Thus, there is a need for a way to increase accuracy of iPPG signals in order to improve the ability to utilize iPPG signals to detect physiological responses.

SUMMARY

Some embodiments described herein utilize sensors, such as head-mounted sensors or remote cameras, to obtain PPG signals from one side or both sides of a user's head. A PPG signal is an optically obtained plethysmogram that is indicative of blood volume changes in the microvascular bed of tissue. A PPG signal is often obtained by using a pulse oximeter, which illuminates the skin and measures changes in light absorption. Another possibility for obtaining the PPG signal is using an imaging photoplethysmography (iPPG) device. As opposed to contact PPG devices, iPPG does not require contact with the skin and is obtained by a non-contact sensor, such as a video camera. Other names known in the art for iPPG include: remote photoplethysmography (rPPG), remote photoplethysmographic imaging, remote imaging photoplethysmography, remote-PPG, and multi-site photoplethysmography (MPPG).

Some embodiments described herein utilize head-mounted contact photoplethysmogram device (PPG device) to obtain a signal (PPG signal), which can be used to improve detection of physiological responses based on iPPG signals. Some examples of physiological responses that may be detected include: an allergic reaction, a stroke, a migraine, stress, a certain emotional response, pain, and blood pressure (i.e., calculating the blood pressure value). Optionally, the improvement is achieved by utilizing timings of fiducial points in the PPG signal in order to extract to extract values from images measured by an iPPG device, which are often noisy (e.g., due to external illumination). Thus, an accurate value from a single signal (PPG signal) may be utilized to extract values for multiple iPPG signals (which may correspond to different regions in the images and/or different sets of pixels in the images).

One aspect of this disclosure involves a system that detects a physiological response. The system includes at least a head-mounted contact photoplethysmography device that measures a signal indicative of photoplethysmogram signal at a first region that comprises exposed skin on a user's head (PPG signal). The system also includes a camera that captures images of a second region that includes exposed skin on the user's head. Optionally, the camera is located more than 10 mm away from the user's head. Optionally, the camera is an inward-facing head-mounted camera, and both the camera and the head-mounted contact photoplethysmography device are physically coupled to smartglasses or to a smart-helmet, which is designed to measure the user in day-to-day activities, over a duration of weeks, months, and/or years. The system also includes a computer that detects a physiological response based on: (i) imaging photoplethysmogram signals (iPPG signals) recognizable in the images, and (ii) correlations between the PPG signal and the iPPG signals.

Another aspect of this disclosure involves a method for detecting a physiological response. In one embodiment, the method includes the following steps: measuring a signal indicative of a photoplethysmogram signal at a first region comprising exposed skin on a user's head (PPG signal) utilizing a head-mounted contact photoplethysmography device; capturing images of a second region comprising exposed skin on the user's head utilizing a camera, where the camera is located more than 10 mm away from the user's head; and detecting a physiological response based on: (i) imaging photoplethysmogram signals (iPPG signals) recognizable in the images, and (ii) correlations between the PPG signal and the iPPG signals.

Yet another aspect of this disclosure include a head-mounted imaging photoplethysmography system. In one embodiment, the system includes a head-mounted contact photoplethysmography device configured to measure a signal indicative of a photoplethysmogram signal at a first region comprising exposed skin on a user's head (PPG signal). The system also includes a head-mounted camera configured to capture images of a second region comprising exposed skin on the user's head, where the camera is located more than 10 mm away from the user's head. The system also include a head-mounted computer configured to: identify times at which fiducial points appear in the PPG signal; calculate, based on the times, time-segments in which the fiducial points are expected to appear in imaging photoplethysmogram signals recognizable the images (iPPG signals); and detect a physiological response based on values of the iPPG signals during the time-segments.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments are herein described by way of example only, with reference to the following drawings:

FIG. 1a illustrates an embodiment of a system that utilizes multiple PPG signals, measured using different types of sensors, to detect a physiological response;

FIG. 1b illustrates smartglasses that include a camera and several contact PPG devices;

FIG. 1c illustrates smartglasses that include at least first, second, and third inward-facing cameras;

FIG. 2 is a schematic illustration of some of the various fiducial points for PPG signals often used in the art;

FIG. 3a and FIG. 3b illustrate various inward-facing head-mounted cameras coupled to an eyeglasses frame;

FIG. 4 illustrates inward-facing head-mounted cameras coupled to an augmented reality device;

FIG. 5 illustrates head-mounted cameras coupled to a virtual reality device;

FIG. 6 illustrates a side view of head-mounted cameras coupled to an augmented reality device;

FIG. 7 illustrates a side view of head-mounted cameras coupled to a sunglasses frame;

FIG. 8, FIG. 9, FIG. 10 and FIG. 11 illustrate head-mounted systems (HMSs) configured to measure various ROIs relevant to some of the embodiments describes herein;

FIG. 12, FIG. 13, FIG. 14 and FIG. 15 illustrate various embodiments of systems that include inward-facing head-mounted cameras having multi-pixel sensors (FPA sensors);

FIG. 16a , FIG. 16b , and FIG. 16c illustrate embodiments of two right and left clip-on devices that are configured to attached/detached from an eyeglasses frame;

FIG. 17a and FIG. 17b illustrate an embodiment of a clip-on device that includes inward-facing head-mounted cameras pointed at the lower part of the face and the forehead;

FIG. 18a and FIG. 18b illustrate embodiments of right and left clip-on devices that are configured to be attached behind an eyeglasses frame;

FIG. 19a and FIG. 19b illustrate an embodiment of a single-unit clip-on device that is configured to be attached behind an eyeglasses frame;

FIG. 20 illustrates embodiments of right and left clip-on devices, which are configured to be attached/detached from an eyeglasses frame, and have protruding arms to hold inward-facing head-mounted cameras;

FIG. 21 illustrates a scenario in which an alert regarding a possible stroke is issued;

FIG. 22a is a schematic illustration of an inward-facing head-mounted camera embedded in an eyeglasses frame, which utilizes the Scheimpflug principle;

FIG. 22b is a schematic illustration of a camera that is able to change the relative tilt between its lens and sensor planes according to the Scheimpflug principle;

FIG. 23 illustrates an embodiment of a system that collects thermal measurements related to respiration, in which four inward-facing head-mounted thermal cameras (CAMs) are coupled to a football helmet;

FIG. 24 illustrates a situation in which an alert is issued to a user when it is detected that the ratio the duration of exhaling and inhaling is too low;

FIG. 25 illustrates an embodiment of a system that collects thermal measurements related to respiration, in which four CAMs are coupled to the bottom of an eyeglasses frame;

FIG. 26a , FIG. 26b , FIG. 27a , FIG. 27b and FIG. 27c illustrate how embodiments described herein may help train an elderly user to exhale during effort;

FIG. 28a and FIG. 28b illustrate a fitness app running on smartphone, which instructs the user to exhale while bending down, and to inhale while straightening up;

FIG. 29 illustrates a fitness app running on smartphone, which instructs the user to stay in a triangle pose for 8 breath cycles;

FIG. 30 illustrates notifying a user about mouth breathing and suggesting to breathe through the nose;

FIG. 31 illustrates an exemplary UI that shows statistics about the dominant nostril and mouth breathing during the day;

FIG. 32 illustrates a virtual robot that the user sees via augmented reality (AR), which urges the user to increase the ratio between the duration of the user's exhales and inhales;

FIG. 33 illustrates an asthmatic patient who receives an alert that his breathing rate increased to an extent that often precedes an asthma attack;

FIG. 34a is a schematic illustration of a left dominant nostril;

FIG. 34b is a schematic illustration of a right dominant nostril;

FIG. 34c is a schematic illustration of balanced breathing;

FIG. 35 is a schematic illustration of an embodiment of a system that identifies the dominant nostril;

FIG. 36a illustrates an embodiment of a system that suggests activities according to the dominant nostril;

FIG. 36b illustrates an embodiment of a system for calculating a respiratory parameter;

FIG. 37a illustrates an embodiment of a system for estimating an aerobic activity parameter;

FIG. 37b illustrates an embodiment of an athletic coaching system;

FIG. 37c illustrates a cycler who receives breathing cues via an earbud;

FIG. 37d illustrates a user receiving coaching instructions while hitting a driver in golf;

FIG. 38 illustrates an embodiment of a system configured to provide neurofeedback and/or breathing biofeedback;

FIG. 39, FIG. 40 and FIG. 41 illustrate an embodiment of eyeglasses with head-mounted thermal cameras, which are able to differentiate between different states of the user based on thermal patterns of the forehead;

FIG. 42 illustrates an embodiment of a clip-on device configured to be attached and detached from a frame of eyeglasses multiple times;

FIG. 43 illustrates a scenario in which a user has neurofeedback session during a day-to-day activity;

FIG. 44a and FIG. 44b illustrate the making of different detections of emotional response based on thermal measurements compared to the emotional response that is visible in a facial expression;

FIG. 45 illustrates an embodiment of a smartphone app that provides a user with feedback about how he/she looks to others;

FIG. 46 illustrates one embodiment of a tablet app that provides the user a feedback about how he/she felt during a certain period;

FIG. 47 illustrates an embodiment of the system configured to detect a physiological response based on facial skin color changes (FSCC);

FIG. 48a and FIG. 48b illustrate heating of a ROI for different reasons: sinusitis (which is detected), and acne (which is not detected as sinusitis);

FIG. 49a and FIG. 49b illustrate an embodiment of a system that provides indications when the user touches his/her face;

FIG. 50a illustrates a first case where a user's hair does not occlude the forehead;

FIG. 50b illustrates a second case where a user's hair occludes the forehead and the system requests the user to move the hair in order to enable correct measurements of the forehead;

FIG. 51a illustrates an embodiment of a system that detects a physiological response based on measurements taken by an inward-facing head-mounted thermal camera and an outward-facing head-mounted thermal camera;

FIG. 51b illustrates a scenario in which a user receives an indication on a GUI that the user is not monitored in direct sunlight;

FIG. 52 illustrates a case in which a user receives an indication that she is not being monitored in a windy environment;

FIG. 53 illustrates an elderly person whose facial temperature increases as a result of bending over;

FIG. 54 illustrates the effect of consuming alcohol on values of thermal measurements;

FIG. 55 illustrates an increase in the thermal measurements due to smoking;

FIG. 56 illustrates a decrease in the thermal measurements due to taking medication; and

FIG. 57a and FIG. 57b are schematic illustrations of possible embodiments for computers.

DETAILED DESCRIPTION

Herein the terms “photoplethysmogram signal”, “photoplethysmographic signal”, “photoplethysmography signal”, and other similar variations are interchangeable and refer to the same type of signal. A photoplethysmogram signal may be referred to as a “PPG signal”, or an “iPPG signal” when specifically referring to a PPG signal obtained from a camera. The terms “photoplethysmography device”, “photoplethysmographic device”, “photoplethysmogram device”, and other similar variations are also interchangeable and refer to the same type of device that measures a signal from which it is possible to extract the photoplethysmogram signal. The photoplethysmography device may be referred to as “PPG device”.

Sentences in the form of “a sensor configured to measure a signal indicative of a photoplethysmogram signal” refer to at least one of: (i) a contact PPG device, such as a pulse oximeter that illuminates the skin and measures changes in light absorption, where the changes in light absorption are indicative of the PPG signal, and (ii) a non-contact camera that captures images of the skin, where a computer extracts the PPG signal from the images using an imaging photoplethysmography (iPPG) technique. Other names known in the art for iPPG include: remote photoplethysmography (rPPG), remote photoplethysmographic imaging, remote imaging photoplethysmography, remote-PPG, and multi-site photoplethysmography (MPPG).

A PPG signal is often obtained by using a pulse oximeter, which illuminates the skin and measures changes in light absorption. Another possibility for obtaining the PPG signal is using an imaging photoplethysmography (iPPG) device. As opposed to contact PPG devices, iPPG does not require contact with the skin and is obtained by a non-contact sensor, such as a video camera.

A time series of values measured by a PPG device, which is indicative of blood flow changes due to pulse waves, is typically referred to as a waveform (or PPG waveform to indicate it is obtained with a PPG device). It is well known that PPG waveforms show significant gender-related differences, age-related differences, and health-related differences. As a result, the PPG waveforms of different people often display different characteristics (e.g., slightly different shapes and/or amplitudes). In addition, the PPG waveform depends on the site at which it is measured, skin temperature, skin tone, and other parameters.

The analysis of PPG signals usually includes the following steps: filtration of a PPG signal (such as applying bandpass filtering and/or heuristic filtering), extraction of feature values from fiducial points in the PPG signal (and in some cases may also include extraction of feature values from non-fiducial points in the PPG signal), and analysis of the feature values.

One type of features that is often used when performing calculations involving PPG signals involves fiducial points related to the waveforms of the PPG signal and/or to functions thereof (such as various derivatives of the PPG signal). There are many known techniques to identify the fiducial points in the PPG signal, and to extract the feature values. The following are some non-limiting examples of how to identify fiducial points.

FIG. 2 is a schematic illustration of some of the various fiducial points often used in the art (and described below). These examples of fiducial points include fiducial points of the PPG signal, fiducial points in the first derivative of the PPG signal (velocity photoplethysmogram, VPG), and fiducial points in the second derivative of the PPG signal (acceleration photoplethysmogram, APG).

Fiducial points in the PPG signal may include: the systolic notch 920, which is the minimum at the PPG signal onset; the systolic peak 921, which is the maximum of the PPG signal; the dicrotic notch 922, which coincident with e 934 (see below at the second derivative of the PPG signal); and the diastolic peak 923, which is the first local maximum of the PPG signal after the dicrotic notch and before 0.8 of the duration of the cardiac cycle, or if there is no such local maximum, then the first local maximum of the second derivative after e and before 0.8 of the duration of the cardiac cycle.

Fiducial points in the first derivative of the PPG signal (velocity photoplethysmogram, VPG) may include: the maximum slope peak in systolic of VPG 925; the local minima slope in systolic of VPG 926; the global minima slope in systolic of VPG 927; and the maximum slope peak in diastolic of VPG 928.

Fiducial points in the second derivative of the PPG signal (acceleration photoplethysmogram, APG) may include: a 930, which is the maximum of APG prior to the maximum of VPG; b 931, which is the first local minimum of APG following a; c 932, which is the greatest maximum of APG between b and e, or if no maxima then the first of (i) the first maximum of VPG after e, and (ii) the first minimum of APG after e; d 933, which is the lowest minimum of APG after c and before e, or if no minima then coincident with c; e 934, which is the second maximum of APG after maximum of VPG and before 0.6 of the duration of the cardiac cycle, unless the c wave is an inflection point, in which case take the first maximum; and f 935, which is the first local minimum of APG after e and before 0.8 of the duration of the cardiac cycle.

Fiducial points in the third derivative of the PPG signal (PPG′″) may include: the first local maximum of PPG′″ after b; and the last local minimum of PPG′″ before d, unless c=d, in which case take the first local minimum of PPG′″ after d, and if there is a local maximum of the PPG signal between this point and the dicrotic notch then use it instead.

Feature values of the PPG signal may also be extracted from relationships in the PPG signal and/or its derivatives. The following are some non-limiting examples such possible feature values: pulse width, peak to peak time, ratio of areas before and after dicrotic notch in a complete cycle, baseline wander (BW), which is the mean of the amplitudes of a beat's peak and trough; amplitude modulation (AM), which is the difference between the amplitudes of each beat's peak and trough; and frequency modulation (FM), which is the time interval between consecutive peaks.

Examples of additional features that can be extracted from the PPG signal, together with schematic illustrations of the feature locations on the PPG signal, can be found in the following three publications: (i) Peltokangas, Mikko, et al. “Parameters extracted from arterial pulse waves as markers of atherosclerotic changes: performance and repeatability.” IEEE journal of biomedical and health informatics 22.3 (2017): 750-757; (ii) Ahn, Jae Mok. “New aging index using signal features of both photoplethysmograms and acceleration plethysmograms.” Healthcare informatics research 23.1 (2017): 53-59; (iii) Charlton, Peter H., et al. “Assessing mental stress from the photoplethysmogram: a numerical study.” Physiological measurement 39.5 (2018): 054001, and (iv) Peralta, Elena, et al. “Optimal fiducial points for pulse rate variability analysis from forehead and finger photoplethysmographic signals.” Physiological measurement 40.2 (2019): 025007.

Although the above mentioned references describe manual feature selection, the features may be selected using any appropriate feature engineering technique, including using automated feature engineering tools that help data scientists to reduce data exploration time, and enable non-experts, who may not be familiar with data science and/or PPG characteristics, to quickly extract value from their data with little effort.

Unless there is a specific reference to a specific derivative of the PPG signal, phrases of the form of “based on the PPG signal” refer to the PPG signal and any derivative thereof, including the first derivative of the PPG signal, the second derivative of the PPG signal, and the third derivative of the PPG signal. For example, a sentence in the form of “a computer configured to detect a physiological signal based on the PPG signal” is to be interpreted as “a computer configured to detect a physiological signal based on at least one of: the PPG signal, a first derivative of the PPG signal, a second derivative of the PPG signal, a the third derivative of the PPG signal, and/or any other derivative of the PPG signal”.

Algorithms for filtration of the PPG signal, extraction of feature values from fiducial points in the PPG signal, and analysis of the feature values extracted from the PPG signal are well known in the art, and can be found for example in the following references: (i) Allen, John. “Photoplethysmography and its application in clinical physiological measurement.” Physiological measurement 28.3 (2007): R1, and also in the thousands of references citing this reference; (ii) Elgendi, Mohamed. “On the analysis of fingertip photoplethysmogram signals.” Current cardiology reviews 8.1 (2012): 14-25, and also in the hundreds of references citing this reference; (iii) Holton, Benjamin D., et al. “Signal recovery in imaging photoplethysmography.” Physiological measurement 34.11 (2013): 1499, and also in the dozens of references citing this reference, (iv) Sun, Yu, and Nitish Thakor. “Photoplethysmography revisited: from contact to noncontact, from point to imaging.” IEEE Transactions on Biomedical Engineering 63.3 (2015): 463-477, and also in the dozens of references citing this reference, (v) Kumar, Mayank, Ashok Veeraraghavan, and Ashutosh Sabharwal. “DistancePPG: Robust non-contact vital signs monitoring using a camera.” Biomedical optics express 6.5 (2015): 1565-1588, and also in the dozens of references citing this reference, (vi) Wang, Wenjin, et al. “Algorithmic principles of remote PPG.” IEEE Transactions on Biomedical Engineering 64.7 (2016): 1479-1491, and also in the dozens of references citing this reference, and (vii) Rouast, Philipp V., et al. “Remote heart rate measurement using low-cost RGB face video: a technical literature review.” Frontiers of Computer Science 12.5 (2018): 858-872, and also in the dozens of references citing this reference.

Various embodiments described herein involve calculations based on machine learning approaches. Herein, the terms “machine learning approach” and/or “machine learning-based approaches” refer to learning from examples using one or more approaches. Examples of machine learning approaches include: decision tree learning, association rule learning, regression models, nearest neighbors classifiers, artificial neural networks, deep learning, inductive logic programming, support vector machines, clustering, Bayesian networks, reinforcement learning, representation learning, similarity and metric learning, sparse dictionary learning, genetic algorithms, rule-based machine learning, and/or learning classifier systems.

Herein, a “machine learning-based model” is a model trained using one or more machine learning approaches. For brevity's sake, at times, a “machine learning-based model” may simply be called a “model”. Referring to a model as being “machine learning-based” is intended to indicate that the model is trained using one or more machine learning approaches (otherwise, “model” may also refer to a model generated by methods other than machine learning).

Herein, “feature values” (also known as feature vector, feature data, and numerical features) may be considered input to a computer that utilizes a model to perform the calculation of a value, such as a value indicative of one or more vital signs of a user. It is to be noted that the terms “feature” and “feature value” may be used interchangeably when the context of their use is clear. However, a “feature” typically refers to a certain type of value, and represents a property, while “feature value” is the value of the property with a certain instance (i.e., the value of the feature in a certain sample).

It is to be noted that when it is stated that feature values are generated based on data comprising multiple sources, it means that for each source, there is at least one feature value that is generated based on that source (and possibly other data). For example, stating that feature values are generated from an image capturing first and second regions (IM_(ROI1) and IM_(ROI2), respectively) means that the feature values include at least a first feature value generated based on IM_(ROI1) and a second feature value generated based on IM_(ROI2).

In addition to feature values generated based on measurements taken by sensors mentioned in a specific embodiment, at least some feature values utilized by a computer of the specific embodiment may be generated based on additional sources of data that were not specifically mentioned in the specific embodiment. Some examples of such additional sources of data include: (i) contextual information such as the time of day (e.g., to account for effects of the circadian rhythm), day of month (e.g., to account for effects of the lunar rhythm), day in the year (e.g., to account for seasonal effects), and/or stage in a menstrual cycle; (ii) information about the user being measured such as sex, age, weight, height, body build, genetics, medical records, and/or intake of substances; (iii) measurements of the environment, such as temperature, humidity level, noise level, elevation, air quality, a wind speed, precipitation, and infrared radiation; and/or (iv) values of physiological signals of the user obtained by sensors that are not mentioned in the specific embodiment, such as an electrocardiogram (ECG) sensor, an electroencephalography (EEG) sensor, a galvanic skin response (GSR) sensor, a movement sensor, an acoustic sensor, and/or a temperature sensor.

A machine learning-based model of a specific embodiment may be trained, in some embodiments, based on data collected in day-to-day, real world scenarios. As such, the data may be collected at different times of the day, while users perform various activities, and in various environmental conditions. Utilizing such diverse training data may enable a trained model to be more resilient to the various effects that different conditions can have on the measurements, and consequently, be able to achieve better detection of a required parameter in real world day-to-day scenarios.

The machine learning-based model may be personalized for a specific user. For example, after receiving a verified diagnosis of an extent of a physiological condition (such as blood pressure level, extent of a cardiovascular disease, extent of a pulmonary disease, extent of a migraine attack, etc.), the computed can use the verified diagnosis as labels and generate from a physiological measurement (such as the PPG signal, the temperature signal, the movement signal, and/or the audio signal) feature values to train a personalized machine learning-based model for the user. Then the computer can utilize the personalized machine learning-based model for future calculations of the extent of the physiological condition based on feature values.

Sentences in the form of “inward-facing head-mounted camera” refer to a camera configured to be worn on a user's head and to remain pointed at its ROI, which is on the user's face, also when the user's head makes angular and lateral movements (such as movements with an angular velocity above 0.1 rad/sec, above 0.5 rad/sec, and/or above 1 rad/sec). A head-mounted camera (which may be inward-facing and/or outward-facing) may be physically coupled to a frame worn on the user's head, may be physically coupled to eyeglasses using a clip-on mechanism (configured to be attached to and detached from the eyeglasses), may be physically coupled to a hat or a helmet, or may be mounted to the user's head using any other known device that keeps the camera in a fixed position relative to the user's head also when the head moves. Sentences in the form of “sensor physically coupled to the frame” mean that the sensor moves with the frame, such as when the sensor is fixed to (or integrated into) the frame, and/or when the sensor is fixed to (or integrated into) an element that is physically coupled to the frame, and/or when the sensor is connected to the frame with a clip-on mechanism.

Sentences in the form of “a frame configured to be worn on a user's head” or “a frame worn on a user's head” refer to a mechanical structure that loads more than 50% of its weight on the user's head. For example, an eyeglasses frame may include two temples connected to two rims connected by a bridge; the frame in Oculus Rift™ includes the foam placed on the user's face and the straps; and the frame in Google Glass™ is similar to an eyeglasses frame. Additionally or alternatively, the frame may connect to, be affixed within, and/or be integrated with, a helmet (e.g., a safety helmet, a motorcycle helmet, a combat helmet, a sports helmet, a bicycle helmet, etc.), goggles, and/or a brainwave-measuring headset.

Sentences in the form of “a frame configured to be worn on a user's head in a consistent manner” refer to a frame that is located in the same position relative to the head when worn repeatedly, and thus sensors attached to that frame are most likely to be positioned each time at the same location relative to the head. For example, eyeglasses frames, goggles, and helmets are all included under the definition of a frame that is worn in a consistent manner. However, a flexible headband, or adhesive sensors that are placed manually one by one, are not worn in a consistent manner, because these sensors are most likely to be positioned each time in a different location relative to the head.

The term “smartglasses” refers to any type of a device that reminds eyeglasses, and includes a frame configured to be worn on a user's head in a consistent manner, and includes electronics to operate one or more sensors. The frame may be an integral part of the smartglasses, and/or an element that is connected to the smartglasses. Examples of smartglasses include: any type of eyeglasses with electronics (whether prescription or plano), sunglasses with electronics, safety goggles with electronics, sports goggle with electronics, augmented reality devices, virtual reality devices, and mixed reality devices. In addition, the term “eyeglasses frame” refers to one or more of the following devices, whether with or without electronics: smartglasses, prescription eyeglasses, plano eyeglasses, prescription sunglasses, plano sunglasses, safety goggles, sports goggle, an augmented reality device, virtual reality devices, and a mixed reality device.

The term “smart-helmet” refers to a helmet that includes a frame configured to be worn on a user's head in a consistent manner, and includes electronics to operate one or more sensors. The frame may be an integral part of the smart-helmet, and/or an element that is connected to the smart-helmet. Examples of smart-helmets include: a safety helmet with electronics, a motorcycle helmet with electronics, a combat helmet with electronics, a sports helmet with electronics, and a bicycle helmet with electronics.

Examples of electronics that may be included in smartglasses and/or a smart-helmet include one or more of the following electronic components: a computer, a microcontroller, a processor, a memory, and a communication interface. The electronics of the smartglasses and/or smart-helmets may be integrated in various ways. For example, the electronics may be integrated into the package of one of the sensors, such as a camera housing that is physically coupled to a helmet, where the housing includes the imaging sensor and its processor, memory, power supply and wireless communication unit. In another example, the electronics may be integrated into the frame, such as a microcontroller, power supply and wireless communication unit that are integrated into an eyeglasses frame, and configured to operate a PPG device and a microphone that are physically coupled to the frame.

The term “Visible-light camera” refers to a non-contact device designed to detect at least some of the visible spectrum, such as a video camera with optical lenses and CMOS or CCD sensor. The term “thermal camera” refers to a non-contact device that measures electromagnetic radiation having wavelengths longer than 2500 nanometer (nm) and does not touch its region of interest (ROI). A thermal camera may include one sensing element (pixel), or multiple sensing elements that are also referred to herein as “sensing pixels”, “pixels”, and/or focal-plane array (FPA). A thermal camera may be based on an uncooled thermal sensor, such as a thermopile sensor, a microbolometer sensor (where microbolometer refers to any type of a bolometer sensor and its equivalents), a pyroelectric sensor, or a ferroelectric sensor.

A reference to a “camera” herein may relate to various types of devices. In one example, a camera may be a visible-light camera. In another example, a camera may capture light in the ultra-violet range. In another example, a camera may capture near infrared radiation (e.g., wavelengths between 750 and 2000 nm). And in still another example, a camera may be a thermal camera.

When a camera is inward-facing and head-mounted, challenges faced by systems known in the art that are used to acquire images, which include non-head-mounted cameras, may be simplified and even eliminated with some of the embodiments described herein. Some of these challenges may involve dealing with complications caused by movements of the user, image registration, region of interest (ROI) alignment, tracking based on hot spots or markers, and motion compensation.

The term “temperature sensor” refers to a device that measures temperature and/or temperature change. The temperature sensor may be a contact thermometer (such as a thermistor, a thermocouple), and/or a non-contact thermal cameras (such as a thermopile sensor, a microbolometer sensor, a pyroelectric sensor, or a ferroelectric sensor). Some examples of temperature sensors useful to measure skin temperature include: thermistors, thermocouples, thermoelectic effect, thermopiles, microbolometers, and pyroelectric sensors. Some examples of temperature sensors useful to measure environment temperature include: thermistors, resistance temperature detectors, thermocouples; thermopiles, and semiconductor-based sensors.

The term “movement sensor” refers to a sensor comprising one or more of the following components: a 3-axis gyroscope, a 3-axis accelerometer, and a 3-axis magnetometer. The movement sensor may also include a sensor that measures barometric pressure.

The term “acoustic sensor” refers to a device that converts sound waves into an electrical signal. An acoustic sensor can be a microphone, such as a dynamic microphone that works via electromagnetic induction, a piezoelectric microphone that uses the phenomenon of piezoelectricity, a fiber-optic microphone that converts acoustic waves into electrical signals by sensing changes in light intensity, a Micro-Electrical-Mechanical System (MEMS) microphone (such as silicon MEMS and piezoelectric MEMS), and/or other sensors that measure sound waves, such as described in the following examples: (i) Han, Jae Hyun, et al. “Basilar membrane-inspired self-powered acoustic sensor enabled by highly sensitive multi tunable frequency band.” Nano Energy 53 (2018): 198-205, describes a self-powered flexible piezoelectric acoustic sensor having high sensitivity, (ii) Rao, Jihong, et al. “Recent Progress in Self-Powered Skin Sensors.” Sensors 19.12 (2019): 2763. describes various self-powered acoustic skin sensors, such as an integrated triboelectric nanogenerator (TENG) with a polymer tube that can pick up and recover human throat voice even in an extremely noisy or windy environment, and (iii) Scanlon, Michael V. Acoustic sensor for voice with embedded physiology. Army Research Lab Adelphi Md., 1999, describes a gel-coupled acoustic sensor able to collect information related to the function of the heart, lungs, and changes in voice patterns.

Herein, the term “blood pressure” is indicative of one or more of the following: the systolic blood pressure of the user, the diastolic blood pressure of the user, and the mean arterial pressure (MAP) of the user. It is specifically noted that the term “blood pressure” is not limited to the systolic and diastolic blood pressure pair.

The terms “substance intake” or “intake of substances” refer to any type of food, beverage, medications, drugs, smoking/inhaling, and any combination thereof.

FIG. 1a illustrates an embodiment of a system that utilizes multiple PPG signals, measured using different types of sensors, to detect a physiological response. In one embodiment, the system includes at least a head-mounted contact PPG device 782, a camera 784, and a computer 780.

In one embodiment, the head-mounted contact PPG device 782 (also referred to as PPG device 782) measures a signal indicative of a PPG signal 783 at a first region of interest (ROI₁) on a user's body (also referred to as PPG signal 783). ROI₁ includes a region of exposed skin on the user's head, and the PPG device 782 includes one or more light sources configured to illuminate ROI₁. For example, the one or more light sources may include light emitting diodes (LEDs) that illuminate ROI₁. Optionally, the one or more LEDs include at least two LEDs, wherein each illuminates ROI₁ with light at a different wavelength. In one example, the at least two LEDs include a first LED that illuminates ROI₁ with green light and a second LED that illuminates ROI₁ with an infrared light. Optionally, the PPG device 782 includes one or more photodetectors configured to detect extents of reflections from ROI₁.

The camera 784 captures images 785 of a second region of interest (ROI₂) on the user's head. The camera is located more than 10 mm away from the user's head. Optionally, the camera is located more than 20 mm away from the user's head. Optionally, the camera 784 is a head-mounted camera. In some embodiments, the camera 784 may utilize a light source to illuminate ROI₂. Optionally, the light source is configured to illuminate at least a portion of ROI₂, and the camera 784 is located more than 15 cm away from the user's head.

In another embodiment, the system illustrated in FIG. 1a does not include a light source that illuminates ROI₂ and the camera 784 may be considered a “passive” camera.

In some embodiments, the camera 784 is not head-mounted. Optionally, the images 785 taken by the non-head mounted camera are synchronized with the PPG signal 783 (e.g., based on synchronizing the clocks of the PPG device 782 and the camera 784, and/or based on time stamps added by the PPG device 782 and time stamps added by the camera 784). Optionally, the system achieves data synchronization that is better than 35 milliseconds between the PPG signal and the iPPG signals. Optionally, the system achieves data synchronization better than 1 millisecond between the PPG signal and the iPPG signals. Examples of cameras that are not head-mounted, which may be synchronized with the head-mounted PPG device 782 include: a smartphone camera, a tablet camera, a laptop camera, and/or webcam.

In some embodiments, references to the camera 784 involve more than one camera. Optionally, the camera 784 may refer to two or more inward-facing head-mounted cameras, and ROI₂ includes two or more regions on the user's head that are respectively captured by the two or more inward-facing head-mounted cameras. Optionally, the two or more regions include regions on different sides of the user's head.

Optionally, ROI₂ covers a larger area of exposed skin than ROI₁. In one example, the area of ROI₂ is at least ten times larger than the area of ROI₁. In one example, the PPG device 782 does not obstruct the field of view of the camera 784 to ROI₂.

In some embodiments, various devices, such as the PPG device 782, the camera 784, and/or the computer 780, may be physically coupled to a frame of smartglasses or to a smart-helmet, which is designed to measure the user in day-to-day activities, over a duration of weeks, months, and/or years. FIG. 1b and FIG. 1c illustrate smartglasses that may be utilized to realize the invention described herein.

FIG. 1b illustrates smartglasses that include camera 796 and several contact PPG devices. The contact PPG devices correspond to the PPG device 782 and are used to measure the PPG signal 783. The contact PPG devices may be coupled at various locations on the frame 794, and thus may come in contact with various regions on the user's head. For example, contact PPG device 791 a is located on the right temple tip, which brings it to contact with a region behind the user's ear (when the user wears the smartglasses). Contact PPG device 791 b is located on the right temple of the frame 794, which puts it in contact with a region on the user's right temple (when wearing the smartglasses). It is to be noted that in some embodiments, in order to bring the contact PPG device close such that it touches the skin, various apparatuses may be utilized, such as spacers (e.g., made from rubber or plastic), and/or adjustable inserts that can help bridge a possible gap between the frame's temple and the user's face. Such an apparatus is spacer 792 which brings contact PPG device 791 b in contact with the user's temple when the user wears the smartglasses. Another possible location for a contact PPG device is the nose bridge, as contact PPG device 791 c is illustrated in the figure. It is to be noted the contact PPG device 791 c may be embedded in the nose bridge (or one of its components), and/or physically coupled to a part of the nose bridge.

FIG. 1c illustrates smartglasses that include at least first, second, and third inward-facing cameras, each of which may correspond to the camera 784. The figure illustrates a frame 797 to which a first inward-facing camera 795 a is coupled above the lens that is in front of the right eye, and a second inward-facing camera 795 b that is coupled to the frame 797 above the lens that is in front of the left eye. The figure also illustrates a third inward facing camera 795 c that is on the left side of the frame 797 and configured to capture images of lower portions of the user's face (e.g., portions of the left cheek).

The computer 780 is configured, in some embodiments, to detect a physiological response based on: (i) imaging photoplethysmogram signals (iPPG signals) recognizable in the images 785, and (ii) correlations between the PPG signal 783 and the iPPG signals. Some examples of physiological responses that may be detected include: an allergic reaction, a stroke, a migraine, stress, a certain emotional response, pain, and blood pressure (i.e., calculating the blood pressure value). Optionally, the computer 780 forwards an indication of a detection of the physiological response 789 to a device of the user and/or to another computer system. Examples of computers that may be utilized to perform this detection are computer 400 or computer 410 illustrated in FIG. 57a and FIG. 57b , respectively.

Herein, sentences of the form “iPPG signal is recognizable in images” refer to effects of blood volume changes due to pulse waves that may be extracted from a series of images of the region. These changes may manifest as color changes to certain regions (pixels) in the images, and may be identified and/or utilized by a computer (e.g., in order to generate a signal indicative of the blood volume at the region). However, these changes need not necessarily be recognizable to the naked eye (e.g., because of their subtlety, the short duration in which they occur, or involvement of light outside of the visible spectrum). For example, blood flow may cause facial skin color changes (FSCC) that corresponds to different concentrations of oxidized hemoglobin due to varying volume of blood at a certain region due to different stages of a cardiac pulse, and/or the different magnitudes of cardiac output.

Herein, detecting the physiological response may mean detecting that the user is experiencing the physiological response, and/or that there is an onset of the physiological response. In the case of the physiological response being associated with one or more values (e.g., blood pressure), detecting the physiological response may mean calculating the one or more values.

In some embodiments, detecting the physiological response may involve calculating one or more of the following values: an indication of whether or not the user is experiencing the physiological response (e.g., whether or not the user is having a stroke), a value indicative of an extent to which the user is experiencing the physiological response (e.g., a level of pain or stress felt by the user), a duration since the onset of the physiological response (a duration since a migraine has started), and a duration until an onset of the physiological response.

In some embodiments, the computer 780 detects the physiological response utilizing previously taken PPG signals of the user (taken with the PPG device 782) and/or previously taken images (taken with the camera) in which previous iPPG signals are recognizable. Having such previous values can assist the computer 780 to detect changes to blood flow that may be indicative of certain physiological responses. In some embodiments, previously taken PPG signals and/or images are used to generate baseline values representing baseline properties of the user's blood flow. Optionally, calculating the baseline values may be done based on previously taken PPG signals and/or images that were measured at least an hour before taking the PPG signal 783 and/or the images 785. Optionally, calculating the baseline values may be done based on previously taken PPG signals and/or images that were measured at least a day before the PPG signal 783 and/or the images 785. Some examples of baseline values may include baseline physiological signal values (e.g., baseline heart rate, blood pressure, or heart rate variability). Other examples of baseline values may include typical values of fiducial points in PPG signals (e.g., magnitudes of systolic peaks) and/or typical relationships between different fiducial points (e.g., typical distance between systolic peaks and dicrotic notches, and the like).

A baseline value may be calculated in various ways. In a first example, the baseline is a function of the average measurements of the user (which include previously taken PPG signals and/or iPPG signals recognizable in previously taken images described above). In a second example, the baseline value may be a function of the situation the user is in, such that previous measurements taken during similar situations are weighted higher than previous measurements taken during less similar situations. A PPG signal may show different characteristics in different situations because of the different mental and/or physiological states of the user in the different situations. As a result, a situation-dependent baseline can improve the accuracy of detecting the physiological response. In a third example, the baseline value may be a function of an intake of some substances (such as food, beverage, medications, and/or drugs), such that previous measurements taken after consuming similar substances are weighted higher than previous measurements taken after not consuming the similar substances, and/or after consuming less similar substances. A PPG signal may show different characteristics after the user consumes different substances because of the different mental and/or physiological states the user may enter after consuming the substances, especially when the substances include things such as medications, drugs, alcohol, and/or certain types of food. As a result, a substance-dependent baseline can improve the accuracy of detecting the physiological response.

There are various ways in which the computer 780 may utilize correlations between the PPG signal 783 and the iPPG signals to detect the physiological response. In some embodiments, the computer 780 may rely on the fact that due to the proximity of ROI₁ and ROI₂ (both being on the head and consequently, close by) the appearances of pulse waves at the different ROIs is highly correlated. This fact may be utilized by the computer 780 to identify fiducial points in the PPG signal 783, which is often a strong signal, and then to identify the corresponding fiducial points in the correlated iPPG signals (that are noisier than the PPG signal). Additionally or alternatively, when a using machine learning-based approach, at least some of the feature values used by the computer 780 may reflect values related to correlations between the PPG signal 783 and the iPPG signals (e.g., values of similarity and/or offsets between the PPG signal 783 and the iPPG signals). Both uses of correlations are elaborated on further below.

It is to be noted that because the PPG device 782 touches and occludes ROI₁, while the camera 784 does not occlude ROI₂, the PPG signal 783 extracted from the PPG device 782 usually has a much better signal-to-noise (SNR) compared to the iPPG signals extracted from the images 785 of ROI₂. In addition, due to the shorter distance between the PPG device 782 and ROI₁, and especially in embodiments where the camera 784 is a passive camera (i.e., does not include a light source to illuminate ROI₂), the PPG signal 783 will typically suffer much less from illumination changes compared to the iPPG signals.

Furthermore, because both ROI₁ and ROI₂ are on the user's head, and because the PPG device 782 and the camera 784 measure the user essentially simultaneously, manifestation of the pulse arrival in the PPG signal 783 and the iPPG signals are typically highly correlated (e.g., the signals exhibit highly correlated pulse arrival times). This correlation enables the computer 780 to utilize pulse fiducial points identified in the PPG signal 783 (which is less noisy than the iPPG signals) to extract information from iPPG signals more efficiently and accurately.

In one embodiment, the computer 780 extracts from the PPG signal 783 one or more values that may serve as a basis to correlate between the PPG signal 783 and the iPPG signals. Optionally, the extracted values are indicative of one or more of the following PPG waveform fiducial points: a systolic peak, a dicrotic notch, a diastolic peak. Optionally, the extracted values may be indicative of a timing of a certain fiducial point (i.e., when it manifests in the PPG signal 783), and/or the magnitude of the PPG signal 783 at the time corresponding to the certain fiducial point. Additionally or alternatively, the extracted values may be indicative of other waveform properties such as an interbeat interval, and a systolic-diastolic peak-to-peak time.

Due to the camera 784 not being in contact with ROI₂, it is often the case that direct identification of the fiducial points in the iPPG signals may be difficult, e.g., due to the excessive noise in the signal because of movements and ambient light. Knowing an identification of fiducial points in the PPG signal 783, such as times of systolic peaks, dicrotic notches, and diastolic peaks, provides useful information for determining when these events are to be expected to manifest in the iPPG signals. The timings of the occurrences of these fiducial points in the PPG signal 783 can serve as a basis according to which fiducial points can be determined in the iPPG signals.

In one embodiment, times corresponding to fiducial points, as determined based on the PPG signal 783, are also used for fiducial points in the iPPG signals. Thus, the magnitudes of the fiducial points in the iPPG signals are taken essentially at the same times of the fiducial points in the PPG signal 783. Such an approach can be especially accurate when ROI₁ and ROI₂ are close to each other, thus it is likely that manifestation of pulse waves occurs at very similar times in ROI₁ and ROI₂, so when, for example, there is a systolic peak in the PPG signal 863, there is also one approximately at the same time in the iPPG signals.

In another embodiment, times corresponding to fiducial points, as determined based on the PPG signal 783, may also be used to determine fiducial points in the iPPG signals, by applying a certain offset to the times. This certain offset may be used to account for the difference between the distances/route blood travels in order to reach ROI₂ as opposed to the distance/route blood travels in order to reach ROI₁.

In one example, an offset used between when a fiducial point (e.g., a systolic peak) occurs in the PPG signal 783, and when it manifests in each of the iPPG signals may be a fixed offset (e.g., an offset that is a function of the relative location of ROI₂ from ROI₁). In another example, different sub-regions of ROI₂ (e.g., corresponding to different pixels in the images 785) may have different offsets that are calculated empirically relative to the timings of the PPG signal. In still another example, the iPPG signals are extracted from the images based on values of time-segments in which the iPPG signals were expected to appear as a function of the locations of respective regions of the iPPG signals relative to the location of the contact PPG device.

An offset used between when a fiducial point (e.g., a systolic peak) occurs in the PPG signal 783, and when it manifests in in each of the iPPG signals may be adjusted to account for blood velocity. For example, the offset may be inversely proportional to the heart rate and/or blood pressure determined from the PPG signal 783. When the heart rate and/or blood pressure increase, this is usually correlated with a higher velocity of blood flow, which will tend to reduce the difference in manifestations of a pulse wave in ROI₁ and ROI₂.

It is to be noted that offsets used between times of fiducial points identified in the PPG signal 783 and the iPPG signals may be user-specific and learned overtime. For example, histograms of the offsets between the maxima in the PPG signal 783 and the maxima of each of the iPPG signals, as observed over multiple pulses of the user, can be aggregated. Based on these histograms, the most frequent offset can be used to represent the difference between when systolic peaks occur in the PPG signal 783 and when it manifests in each of the iPPG signals.

In another embodiment, times corresponding to fiducial points, as determined based on the PPG signal 783, may be used to set a range of times during which the same fiducial point is expected to manifest in an iPPG signal (from among the iPPG signals). For example, if a systolic peak is observed at time t in the PPG signal 783, a manifestation of a systolic peak will be extracted from a time that falls in [t+a, t+b], where a<b, and the values of a and b are set to correspond to the minimum and maximum offsets between manifestations of systolic peaks in ROI and a sub-region of ROI₂ to which the iPPG signal corresponds. As discussed above, the values a and b may also be adjusted according to values such as the heart rate and/or blood pressure, and may also be learned for a specific user.

In some embodiments, the computer 780 may utilize the PPG signal 783 to verify the quality of the iPPG signals. Optionally, the computer 780 may refrain from utilizing iPPG signals in calculations when they exhibit a significant difference from the PPG signal 783. For example, if a heart rate calculated based on the PPG signal 783, during a certain period, is significantly different from a heart rate calculated based on the iPPG signals during that period (e.g., a difference greater than a threshold of ±5 bpm), then that may indicate the iPPG signals during the certain period were noisy and/or unreliable.

Additionally, using the PPG signal 783, as described above, to assess various sub-regions of ROI₂, can serve as a quality filter to select which regions of the face should be used to perform detection of physiological responses. If a certain region displays consistently an accurate iPPG signal, it may be more reliable for detection of the physiological response than a region from which an accurate signal cannot be extracted.

Another way to describe the benefit of measuring simultaneously the PPG signal 783 and iPPG signals on the head involves the fact that often the iPPG signals are weak relative to the noise. Therefore, automatic detection of the iPPG signals requires discrimination between true PPG pulses and random fluctuations due to the noise. In one embodiment, an algorithm for the selection of the iPPG pulses is based on the values of time-segments in which the iPPG signals are expected to appear as a function of their location relative to the location of the PPG device 782. Optionally, the detected iPPG signals in these time-segments are identified as iPPG signals if they meet one or more criteria based on (i) the spatial waveform of the iPPG signals relative to the reference PPG signal, (ii) correlation between each iPPG signal in the current time-segment and a predetermined number of neighboring time-segments, and (iii) correlations between iPPG signals extracted from neighboring regions of exposed skin on the head, which are expected to show essentially the same rhythm with a bounded time delay. Optionally, the signals are taken as iPPG signals if minimal values of the criteria are obtained in several time-segments. The minimal values and the number of time-segments can be determined in order to achieve minimal standard deviation of the differences between the values of the heart rate extracted from the noisy iPPG signals and the reference heart rate extracted from the less noisy PPG signal.

In some embodiments, the iPPG signals include multiple values for different sub-regions of ROI₂, and the physiological response is detected based on differences between amplitudes of the values recognizable in the different sub-regions of ROI₂. For example, each sub-region may be captured by a subset of pixels in the images 785.

In one embodiment, the physiological response is indicative of an allergic reaction, and the sub-regions of ROI₂ include portions of at least two of the following areas on the user's face: nose, upper lip, lips, cheeks, temples, periorbital area around the eyes, and the forehead. Optionally, the computer 780 detects the allergic reaction based on changes in blood flow which manifest in iPPG signals corresponding to the at least two areas.

In another embodiment, the physiological response is indicative of a stroke, and the sub-regions of ROI₂ include at least one of the following pairs on the user's face: left and right cheeks, left and right temples, left and right sides of the forehead, and left and right sides of the periorbital area around the eyes. Optionally, the computer 780 detects the stroke based on a difference in blood flow on the two sides of the face.

In yet another embodiment, the physiological response is indicative of a migraine, and the sub-regions of ROI₂ include at least one of the following pairs on the user's face: left and right sides of the forehead, left and right temples, left and right sides of the periorbital area around the eyes, and left and right cheeks.

In still another embodiment, the physiological response is indicative of a blood pressure value that is calculated based on differences in pulse transit times detectable in the sub-regions of ROI₂. Optionally, the sub-regions comprise at least two of the following areas on the user's face: left temple, right temple, left side of the forehead, right side of the forehead, left check, right cheek, nose, periorbital area around the left eye, and periorbital area around the right eye.

And in yet another embodiment, the physiological response is indicative of at least one of stress, emotional response, and pain, which are calculated based on changes to hemoglobin concentrations observable in the iPPG signals relative to previous measurements of hemoglobin concentrations observable in the iPPG signals of the user. Optionally, the sub-regions of ROI₂ include at least two of the following areas on the user's face: lips, upper lip, chin, left temple, right temple, left side of the forehead, right side of the forehead, left check, right cheek, left ear lobe, right ear lobe, nose, periorbital area around the left eye, and periorbital area around the right eye.

In one embodiment, the computer 780 is a head-mounted computer. Optionally, detecting the physiological response involves performing at least the following: identifying times at which fiducial points appear in the PPG signal; calculating, based on the times, time-segments in which the fiducial points are expected to appear in imaging photoplethysmogram signals recognizable the images (iPPG signals); and detecting a physiological response based on values of the iPPG signals during the time-segments.

As part of the calculations involved in detecting the physiological response, the computer 780 may perform various filtering and/or processing procedures to the PPG signal 783, the images 785, and/or iPPG signals extracted from the images 785. Some non-limiting examples of the preprocessing include: normalization of pixel intensities (e.g., to obtain a zero-mean unit variance time series signal), and conditioning a time series signal by constructing a square wave, a sine wave, or a user defined shape, such as that obtained from an ECG signal or a PPG signal as described in U.S. Pat. No. 8,617,081.

In some embodiments, the images 785 may undergo various preprocessing to improve the signal, such as color space transformation (e.g., transforming RGB images into a monochromatic color or images in a different color space), blind source separation using algorithms such as independent component analysis (ICA) or principal component analysis (PCA), and various filtering techniques, such as detrending, bandpass filtering, and/or continuous wavelet transform (CWT). Various preprocessing techniques known in the art that may assist in extracting iPPG signals from images are discussed in Zaunseder et al. (2018), “Cardiovascular assessment by imaging photoplethysmography-a review”, Biomedical Engineering 63(5), 617-634. An example of preprocessing that may be used in some embodiments is given in U.S. Pat. No. 9,020,185, titled “Systems and methods for non-contact heart rate sensing”, which describes how a times-series signals obtained from video of a user can be filtered and processed to separate an underlying pulsing signal by, for example, using an ICA algorithm.

In some embodiments, detection of the physiological response may involve calculation of pulse arrival times (PATs) at ROI₁ and/or at one or more sub-regions of ROI₂. Optionally, a PAT calculated from an PPG signal represents a time at which the value representing blood volume (in the waveform represented in the PPG) begins to rise (signaling the arrival of the pulse). Alternatively, the PAT may be calculated as a different time, with respect to the pulse waveform, such as the time at which a value representing blood volume reaches a maximum or a certain threshold, or the PAT may be the average of the time the blood volume is above a certain threshold. Another approach that may be utilized to calculate a PAT from an iPPG signal is described in Sola et al. “Parametric estimation of pulse arrival time: a robust approach to pulse wave velocity”, Physiological measurement 30.7 (2009): 603, which describe a family of PAT estimators based on the parametric modeling of the anacrotic phase of a pressure pulse.

Detection of the physiological response may involve the computer utilizing an approach that may be characterized as involving machine learning. In some embodiments, such a detection approach may involve the computer generating feature values based on data that includes the PPG signal 783, the images 785, and/or iPPG signals recognizable in the images 785, and optionally other data. Optionally, at least some of the feature values are based on correlations between the PPG signal 783 and the iPPG signals. The computer 780 then utilizes a previously trained model 779 to calculate one or more values indicative of whether, and/or to what extent, the user is experiencing the physiological response (which may be any one of the examples of values mentioned further above as being calculated by the computer 780 for this purpose).

Feature values generated based on PPG signals (e.g., the PPG signal 783 and/or one or more of the iPPG signals extracted from the images 785) may include various types of values, which may be indicative of dynamics of the blood flow at the respective regions to which the PPG signals correspond. Optionally, these feature values may relate to properties of a pulse waveform, which may be a specific pulse waveform (which corresponds to a certain beat of the heart), or a window of pulse waveforms (e.g., an average property of pulse waveforms in a certain window of time).

Some examples of feature values that may be generated based on a pulse waveform include: the area under the pulse waveform, the amplitude of the pulse waveform, a derivative and/or second derivative of the pulse waveform, a pulse waveform shape, pulse waveform energy, and pulse transit time (to the respective ROI). Optionally, some feature values may be derived from fiducial points identified in the PPG signals; these may include values such as magnitudes of the PPG signal at certain fiducial points, time offsets between different fiducial points, and/or other differences between fiducial points. Some examples of fiducial point-based feature values may include one or more of the following: a magnitude of a systolic peak, a magnitude of a diastolic peak, duration of the systolic phase, and duration of the diastolic phase. Additional examples of feature values may include properties of the cardiac activity, such as the heart rate and heart rate variability (as determined from the PPG signal). Additionally, some feature values may include values of other physiological signals that may be calculated based on PPG signals, such as blood pressure and cardiac output.

The aforementioned feature values may be calculated in various ways. In one example, some feature values are calculated for each PPG signal individually. In another example, some feature values are calculated after normalizing a PPG signal with respect to previous measurements from the corresponding PPG device used to measure the PPG signal. In other examples, at least some of the feature values may be calculated based on an aggregation of multiple PPG signals (e.g., different pixels/regions in images captured by an iPPG device), or by aggregating values from multiple contact PPG devices.

In some embodiments, at least some of the feature values may include values indicative of correlations between the PPG signal 783 and iPPG signals extracted from the images 785. In one example, the feature values may include values indicative of offsets between when certain fiducial points appear in the PPG signal 783, and when they appear in each of the iPPG signals. In another example, the feature values may include values indicative of offsets at which the correlation (e.g., as calculated by a dot-product) between the PPG signal 783 and the iPPG signals is maximized. In still another example, the feature values may include values indicative of maximal value of correlation (e.g., as calculated by a dot-product) between the PPG signal 783 and the iPPG signals (when using different offsets).

In some embodiments, at least some of the feature values may represent comparative values, which provide an indication of the difference in blood flow, and/or in some other property that may be derived from a PPG signal, between various regions on the head. Optionally, such feature values may assist in detecting asymmetrical blood flow (and/or changes thereto).

In some embodiments, at least some of the feature values describe properties of pulse waveforms (e.g., various types of feature values mentioned above), which are derived from the previous measurements of the user using the PPG device 782 and/or the camera 784. Optionally, these feature values may include various blood flow baselines for the user, which correspond to a certain situation the user was in when the previous measurements were taken.

In some embodiments, at least some of the feature values may be “raw” or minimally processed measurements of the PPG device 782 and/or the camera 784. Optionally, at least some of the feature values may be pixel values obtained by the camera 864. Optionally, the pixel values may be provided as input to functions in order to generate the feature values that are low-level image-based features. Some examples of low-level features, which may be derived from images, include feature generated using Gabor filters, local binary patterns (LBP) and their derivatives, algorithms such as SIFT and/or SURF (and their derivatives), image keypoints, histograms of oriented gradients (HOG) descriptors, and products of statistical procedures such independent component analysis (ICA), principal component analysis (PCA), or linear discriminant analysis (LDA). Optionally, one or more of the feature values may be derived from multiple images taken at different times, such as volume local binary patterns (VLBP), cuboids, and/or optical strain-based features. In one example, one or more of the feature values may represent a difference between values of pixels at one time t and values of other pixels at a different region at some other time t+x (which, for example, can help detect different arrival times of a pulse wave).

In some embodiments, at least some feature values may be generated based on other data sources (in addition to PPG signals). In some examples, at least some feature values may be generated based on other sensors, such as movement sensors (which may be head-mounted, wrist-worn, or carried by the user some other way), head-mounted thermal cameras, or other sensors used to measure the user. In other examples, at least some feature values may be indicative of environmental conditions, such as the temperature, humidity, and/or extent of illumination (e.g., as obtained utilizing an outward-facing head-mounted camera). Additionally, some feature values may be indicative of physical characteristics of the user, such as age, sex, weight, Body Mass Index (BMI), skin tone, and other characteristics and/or situations the user may be in (e.g., level of tiredness, consumptions of various substances, etc.)

Stress is a factor that can influence the diameter of the arteries, and thus influence calculated values that relate to the PPG signals and/or blood flow. In one embodiment, the computer 780 receives a value indicative of a stress level of the user, and generates at least one of the feature values based on the received value. Optionally, the value indicative of the stress level is obtained using a thermal camera. In one example, the system may include an inward-facing head-mounted thermal camera that takes measurements of a periorbital region of the user, where the measurements of a periorbital region of the user are indicative of the stress level of the user. In another example, the system includes an inward-facing head-mounted thermal camera that takes measurements of a region on the forehead of the user, where the measurements of the region on the forehead of the user are indicative of the stress level of the user. In still another example, the system includes an inward-facing head-mounted thermal camera that takes measurements of a region on the nose of the user, where the measurements of the region on the nose of the user are indicative of the stress level of the user.

Hydration is a factor that affects blood viscosity, which can affect the speed at which the blood flows in the body. In one embodiment, the computer 780 receives a value indicative of a hydration level of the user, and generates at least one of the feature values based on the received value. Optionally, the system includes an additional camera that detects intensity of radiation that is reflected from a region of exposed skin of the user, where the radiation is in spectral wavelengths chosen to be preferentially absorbed by tissue water. In one example, said wavelengths are chosen from three primary bands of wavelengths of approximately 1100-1350 nm, approximately 1500-1800 nm, and approximately 2000-2300 nm. Optionally, measurements of the additional camera are utilized by the computer as values indicative of the hydration level of the user.

The following are examples of embodiments that utilize additional inputs to generate feature values used to detect the physiological response. In one embodiment, the computer 780 receives a value indicative of a temperature of the user's body, and generates at least one of the feature values based on the received value. In another embodiment, the computer 780 receives a value indicative of a movement of the user's body, and generates at least one of the feature values based on the received value. For example, the computer 780 may receive the input form a head-mounted Inertial Measurement Unit (IMU 778) that includes a combination of accelerometers, gyroscopes, and optionally magnetometers, and/or an IMU in a mobile device carried by the user. In yet another embodiment, the computer 780 receives a value indicative of an orientation of the user's head, and generates at least one of the feature values based on the received value. For example, the computer 780 may receive the values indicative of the head's orientation from an outward-facing head-mounted camera, and/or from a nearby non-wearable video camera. In still another embodiment, the computer 780 receives a value indicative of consumption of a substance by the user, and generates at least one of the feature values based on the received value. Optionally, the substance comprises a vasodilator and/or a vasoconstrictor.

The model 779 utilized to detect the physiological response may be generated, in some embodiments, based on data obtained from one or more users. In the case where the physiological response is a certain medical condition (e.g., an allergic reaction and/or a migraine), at least some of the data used to train the model 779 corresponds to times in which the one or more users were not affected by the physiological response, and additional data used to train the model was obtained while the physiological response occurred and/or following that time. Thus, this training data may reflect PPG signals and/or blood flow both at normal times, and changes to PPG signals and/or blood flow that may ensue due to the physiological response. In the case where the physiological response corresponds to a value of a physiological signal (e.g., blood pressure), data used to train the model 779 may include measurements of the one or more users that are associated with a reference value for the physiological signal (e.g., the reference values may be blood pressure values measured by an external device).

The aforementioned training data may be used to generate samples, each sample including feature values generated based on PPG signals of a certain user, additional optional data (as described above), and a label. The PPG signals include measurements of the certain user (e.g., taken with the PPG device 782 and the camera 784) at a certain time, and optionally previous measurements of the user taken before the certain time. The label is a value related to the physiological response (e.g., an indication of the extent of the physiological response). For example, the label may be indicative of whether the user, at the certain time, experienced a certain physiological response (e.g., an allergic reaction or a stroke). In another example, the label may be indicative of the extent or severity of the physiological response at the certain time. In yet another example, the label may be indicative of the duration until an onset of the physiological response. In still another example, the label may be indicative of the duration that has elapsed since the onset of the physiological response.

In some embodiments, the model 779 used by the computer 780 to detect the physiological response of a specific user may be generated, at least in part, based on data that includes previous measurements of the specific user (and as such, may be considered personalized to some extent for the specific user). Additionally or alternatively, in some embodiments, the model 779 may be generated based on data of other users. Optionally, the data used to train the model 779 may include data obtained from a diverse set of users (e.g., users of different ages, weights, sexes, preexisting medical conditions, etc.). Optionally, the data used to train the model 779 includes data of other users with similar characteristics to the specific user (e.g., similar weight, age, sex, height, and/or preexisting condition).

In order to achieve a robust model, which may be useful for detecting the physiological response for a diverse set of conditions, in some embodiments, the samples used for the training of the model 779 may include samples based on data collected when users were in different conditions. Optionally, the samples are generated based on data collected on different days, while indoors and outdoors, and while different environmental conditions persisted. In one example, the model 779 is trained on samples generated from a first set of training data taken during daytime, and is also trained on other samples generated from a second set of training data taken during nighttime. In a second example, the model 779 is trained on samples generated from a first set of training data taken while users were exercising and moving, and is also trained on other samples generated from a second set of data taken while users were sitting and not exercising.

Utilizing the model 779 to detect the physiological response may involve the computer 780 performing various operations, depending on the type of model. The following are some examples of various possibilities for the model 779 and the type of calculations that may be accordingly performed by the computer 780, in some embodiments, in order to calculate a certain value indicative of an extent of the physiological response experienced by the user: (a) the model 779 comprises parameters of a decision tree. Optionally, the computer 780 simulates a traversal along a path in the decision tree, determining which branches to take based on the feature values. The certain value may be obtained at the leaf node and/or based on calculations involving values on nodes and/or edges along the path; (b) the model 779 comprises parameters of a regression model (e.g., regression coefficients in a linear regression model or a logistic regression model). Optionally, the computer 780 multiplies the feature values (which may be considered a regressor) with the parameters of the regression model in order to obtain the certain value; and/or (c) the model 779 comprises parameters of a neural network. For example, the parameters may include values defining at least the following: (i) an interconnection pattern between different layers of neurons, (ii) weights of the interconnections, and (iii) activation functions that convert each neuron's weighted input to its output activation. Optionally, the computer 780 provides the feature values as inputs to the neural network, computes the values of the various activation functions and propagates values between layers, and obtains an output from the network, which is the certain value

In some embodiments, a machine learning approach that may be applied to calculating a value indicative of the extent of the physiological response experienced by the user may be characterized as “deep learning”. In one embodiment, the model 779 may include parameters describing multiple hidden layers of a neural network. Optionally, the model 779 may include a convolution neural network (CNN). In one example, the CNN may be utilized to identify certain patterns in the images 785, such as the patterns of corresponding to blood volume effects and ballistocardiographic effects of the cardiac pulse. Due to the fact that calculating the value indicative of the extent of the physiological response may be based on multiple, possibly successive, images that display a certain pattern of change over time (i.e., across multiple frames), these calculations may involve retaining state information that is based on previous images. Optionally, the model 779 may include parameters that describe an architecture that supports such a capability. In one example, the model 779 may include parameters of a recurrent neural network (RNN), which is a connectionist model that captures the dynamics of sequences of samples via cycles in the network's nodes. This enables RNNs to retain a state that can represent information from an arbitrarily long context window. In one example, the RNN may be implemented using a long short-term memory (LSTM) architecture. In another example, the RNN may be implemented using a bidirectional recurrent neural network architecture (BRNN).

In some embodiments, the system illustrated in FIG. 1a may optionally include a head-mounted sensor 788 configured to measure a signal indicative of timing of the user's inhalation phase and/or exhalation phase (respiratory-phase signal). Optionally, the computer 780 may utilize the respiratory-phase signal to detect the physiological response. For example, the computer 780 may utilize correlations between timings of fiducial points of the iPPG signals and the respiratory-phase signal. Optionally, at least some of the feature values generated by the computer 780 (when the detection of the physiological response involves a machine learning-based approach) may be generated based on the respiratory-phase signal. For example, the feature values may include values indicating whether a certain fiducial point occurred while the user was inhaling or exhaling. The head-mounted sensor 788 used to measure the respiratory-phase signal may include one or more of the following sensors: (i) an inward-facing camera configured to take video in which movements of the nostrils and/or lips are indicative of the respiratory-phase signal, (ii) an inward-facing thermal camera configured to measure temperatures of the upper lip and/or the mouth, which are indicative of the respiratory-phase signal, and (iii) an acoustic sensor configured to record sound waves that are indicative of the respiratory-phase signal.

In addition to detecting a physiological response, the system illustrated in FIG. 1a may be utilized to authenticate the user. In one embodiment, the camera 784 is integrated in a non-wearable device (e.g., a smartphone or a tablet computer), and the computer 780 may authenticate the identity of the user and determine that the user is using the non-wearable device by checking whether correlations between the PPG signal and the iPPG signals reaches a predetermined threshold. Optionally, the predetermined threshold indicates, above a predetermined certainty, that the PPG signal 783 and the images 785 (in which the iPPG signals are recognizable) belong to the same person.

The following method for detecting physiological response may be used by systems modeled according to FIG. 1a . The steps described below may be performed by running a computer program having instructions for implementing the method. Optionally, the instructions may be stored on a computer-readable medium, which may optionally be a non-transitory computer-readable medium. In response to execution by a system including a processor and memory, the instructions cause the system to perform the following steps:

In Step 1, measuring a signal indicative of a PPG signal at a first region that includes exposed skin on a user's head (referred to as a PPG signal) utilizing a head-mounted contact PPG device. In one example, the head-mounted contact PPG device is the PPG device 782.

In Step 2, capturing images of a second region that includes exposed skin on the user's head utilizing a camera. Optionally, the camera is located more than 10 mm away from the user's head. Optionally, the camera used in this step is the camera 784.

And in Step 3, detecting a physiological response based on: (i) imaging photoplethysmogram signals (iPPG signals) recognizable in the images, and (ii) correlations between the PPG signal and the iPPG signals.

In some embodiments, detecting the physiological response is done utilizing a machine learning-based approach. Optionally, the method includes the following steps: generating feature values based on data that includes: (i) the iPPG signals, and (ii) correlations between the PPG signal and the iPPG signals; and utilizing a model to calculate, based on the feature values, a value indicative of the extent of the physiological response experienced by the user.

In one embodiment, the physiological response is indicative of a value of blood pressure, and is calculated based on differences in pulse transit times detectable in iPPG signals of sub-regions of the second region. Optionally, the sub-regions include at least two of the following areas on the user's face: left temple, right temple, left side of the forehead, right side of the forehead, left check, right cheek, nose, periorbital area around the left eye, and periorbital area around the right eye.

In another embodiment, the physiological response is indicative of at least one of stress, an emotional response, and pain, which are calculated based on changes to hemoglobin concentrations observable in the iPPG signals relative to previous measurements of hemoglobin concentrations observable in the iPPG signals of the user. Optionally, the sub-regions comprise at least two of the following areas on the user's face: lips, upper lip, chin, left temple, right temple, left side of the forehead, right side of the forehead, left check, right cheek, left ear lobe, right ear lobe, nose, periorbital area around the left eye, and periorbital area around the right eye.

In one embodiment, a low-power head-mounted iPPG system includes: (i) a head-mounted contact PPG device configured to measure a signal indicative of a PPG signal at a first region comprising exposed skin on a user's head (PPG signal), (ii) a head-mounted camera configured to capture images of a second region comprising exposed skin on the user's head; wherein the camera is located more than 10 mm away from the user's head; and (iii) a head-mounted computer configured to efficiently extract iPPG signals from the images based on focusing the iPPG calculations around pulse timings extracted from the PPG signal.

In one embodiment, a head-mounted iPPG system includes: (i) a head-mounted contact PPG device configured to measure a signal indicative of PPG signal at a first region comprising exposed skin on a user's head, (ii) a head-mounted camera configured to capture images of a second region comprising exposed skin on the user's head; wherein the camera is located more than 10 mm away from the user's head; and (iii) a head-mounted computer configured to: identify times at which fiducial points appear in the PPG signal; calculate, based on the times, time-segments in which the fiducial points are expected to appear in iPPG signals recognizable the images; and detect a physiological response based on values of the iPPG signals during the time-segments.

The following is description of additional aspects of embodiments of systems configured to detect physiological responses, including embodiments for various systems that may detect physiological responses based on thermal measurements and/or other sources of data.

A “thermal camera” refers herein to a non-contact device that measures electromagnetic radiation having wavelengths longer than 2500 nanometer (nm) and does not touch its region of interest (ROI). A thermal camera may include one sensing element (pixel), or multiple sensing elements that are also referred to herein as “sensing pixels”, “pixels”, and/or focal-plane array (FPA). A thermal camera may be based on an uncooled thermal sensor, such as a thermopile sensor, a microbolometer sensor (where microbolometer refers to any type of a bolometer sensor and its equivalents), a pyroelectric sensor, or a ferroelectric sensor.

Sentences in the form of “thermal measurements of an ROI” (usually denoted TH_(ROI) or some variant thereof) refer to at least one of: (i) temperature measurements of the ROI (T_(ROI)), such as when using thermopile or microbolometer sensors, and (ii) temperature change measurements of the ROI (ΔT_(ROI)), such as when using a pyroelectric sensor or when deriving the temperature changes from temperature measurements taken at different times by a thermopile sensor or a microbolometer sensor.

In some embodiments, a device, such as a thermal camera, may be positioned such that it occludes an ROI on the user's face, while in other embodiments, the device may be positioned such that it does not occlude the ROI. Sentences in the form of “the system/camera does not occlude the ROI” indicate that the ROI can be observed by a third person located in front of the user and looking at the ROI, such as illustrated by all the ROIs in FIG. 9, FIG. 13 and FIG. 21. Sentences in the form of “the system/camera occludes the ROI” indicate that some of the ROIs cannot be observed directly by that third person, such as ROIs 19 and 37 that are occluded by the lenses in FIG. 3a , and ROIs 97 and 102 that are occluded by cameras 91 and 96, respectively, in FIG. 11.

Although many of the disclosed embodiments can use occluding thermal cameras successfully, in certain scenarios, such as when using an HMS on a daily basis and/or in a normal day-to-day setting, using thermal cameras that do not occlude their ROIs on the face may provide one or more advantages to the user, to the HMS, and/or to the thermal cameras, which may relate to one or more of the following: esthetics, better ventilation of the face, reduced weight, simplicity to wear, and reduced likelihood to being tarnished.

A “Visible-light camera” refers to a non-contact device designed to detect at least some of the visible spectrum, such as a camera with optical lenses and CMOS or CCD sensor.

The term “inward-facing head-mounted camera” refers to a camera configured to be worn on a user's head and to remain pointed at its ROI, which is on the user's face, also when the user's head makes angular and lateral movements (such as movements with an angular velocity above 0.1 rad/sec, above 0.5 rad/sec, and/or above 1 rad/sec). A head-mounted camera (which may be inward-facing and/or outward-facing) may be physically coupled to a frame worn on the user's head, may be attached to eyeglass using a clip-on mechanism (configured to be attached to and detached from the eyeglasses), or may be mounted to the user's head using any other known device that keeps the camera in a fixed position relative to the user's head also when the head moves. Sentences in the form of “camera physically coupled to the frame” mean that the camera moves with the frame, such as when the camera is fixed to (or integrated into) the frame, or when the camera is fixed to (or integrated into) an element that is physically coupled to the frame. The abbreviation “CAM” denotes “inward-facing head-mounted thermal camera”, the abbreviation “CAM_(out)” denotes “outward-facing head-mounted thermal camera”, the abbreviation “VCAM” denotes “inward-facing head-mounted visible-light camera”, and the abbreviation “VCAM_(out)” denotes “outward-facing head-mounted visible-light camera”.

Sentences in the form of “a frame configured to be worn on a user's head” or “a frame worn on a user's head” refer to a mechanical structure that loads more than 50% of its weight on the user's head. For example, an eyeglasses frame may include two temples connected to two rims connected by a bridge; the frame in Oculus Rift™ includes the foam placed on the user's face and the straps; and the frames in Google Glass™ and Spectacles by Snap Inc. are similar to eyeglasses frames. Additionally or alternatively, the frame may connect to, be affixed within, and/or be integrated with, a helmet (e.g., sports, motorcycle, bicycle, and/or combat helmets) and/or a brainwave-measuring headset.

When a thermal camera is inward-facing and head-mounted, challenges faced by systems known in the art that are used to acquire thermal measurements, which include non-head-mounted thermal cameras, may be simplified and even eliminated with some of the embodiments described herein. Some of these challenges may involve dealing with complications caused by movements of the user, image registration, ROI alignment, tracking based on hot spots or markers, and motion compensation in the IR domain.

In various embodiments, cameras are located close to a user's face, such as at most 2 cm, 5 cm, 10 cm, 15 cm, or 20 cm from the face (herein “cm” denotes to centimeters). The distance from the face/head in sentences such as “a camera located less than 15 cm from the face/head” refers to the shortest possible distance between the camera and the face/head. The head-mounted cameras used in various embodiments may be lightweight, such that each camera weighs below 10 g, 5 g, 1 g, and/or 0.5 g (herein “g” denotes to grams).

The following figures show various examples of HMSs equipped with head-mounted cameras. FIG. 3a illustrates various inward-facing head-mounted cameras coupled to an eyeglasses frame 15. Cameras 10 and 12 measure regions 11 and 13 on the forehead, respectively. Cameras 18 and 36 measure regions on the periorbital areas 19 and 37, respectively. The HMS further includes an optional computer 16, which may include a processor, memory, a battery and/or a communication module. FIG. 3b illustrates a similar HMS in which inward-facing head-mounted cameras 48 and 49 measure regions 41 and 41, respectively. Cameras 22 and 24 measure regions 23 and 25, respectively. Camera 28 measures region 29. And cameras 26 and 43 measure regions 38 and 39, respectively.

FIG. 4 illustrates inward-facing head-mounted cameras coupled to an augmented reality device such as Microsoft HoloLens™. FIG. 5 illustrates head-mounted cameras coupled to a virtual reality device such as Facebook's Oculus Rift™. FIG. 6 is a side view illustration of head-mounted cameras coupled to an augmented reality device such as Google Glass™. FIG. 7 is another side view illustration of head-mounted cameras coupled to a sunglasses frame.

FIG. 8 to FIG. 11 illustrate HMSs configured to measure various ROIs relevant to some of the embodiments describes herein. FIG. 8 illustrates a frame 35 that mounts inward-facing head-mounted cameras 30 and 31 that measure regions 32 and 33 on the forehead, respectively. FIG. 9 illustrates a frame 75 that mounts inward-facing head-mounted cameras 70 and 71 that measure regions 72 and 73 on the forehead, respectively, and inward-facing head-mounted cameras 76 and 77 that measure regions 78 and 79 on the upper lip, respectively. FIG. 10 illustrates a frame 84 that mounts inward-facing head-mounted cameras 80 and 81 that measure regions 82 and 83 on the sides of the nose, respectively. And FIG. 11 illustrates a frame 90 that includes (i) inward-facing head-mounted cameras 91 and 92 that are mounted to protruding arms and measure regions 97 and 98 on the forehead, respectively, (ii) inward-facing head-mounted cameras 95 and 96, which are also mounted to protruding arms, which measure regions 101 and 102 on the lower part of the face, respectively, and (iii) head-mounted cameras 93 and 94 that measure regions on the periorbital areas 99 and 100, respectively.

FIG. 12 to FIG. 15 illustrate various inward-facing head-mounted cameras having multi-pixel sensors (FPA sensors), configured to measure various ROIs relevant to some of the embodiments describes herein. FIG. 12 illustrates head-mounted cameras 120 and 122 that measure regions 121 and 123 on the forehead, respectively, and mounts head-mounted camera 124 that measure region 125 on the nose. FIG. 13 illustrates head-mounted cameras 126 and 128 that measure regions 127 and 129 on the upper lip, respectively, in addition to the head-mounted cameras already described in FIG. 12. FIG. 14 illustrates head-mounted cameras 130 and 132 that measure larger regions 131 and 133 on the upper lip and the sides of the nose, respectively. And FIG. 15 illustrates head-mounted cameras 134 and 137 that measure regions 135 and 138 on the right and left cheeks and right and left sides of the mouth, respectively, in addition to the head-mounted cameras already described in FIG. 14.

In some embodiments, the head-mounted cameras may be physically coupled to the frame using a clip-on device configured to be attached/detached from a pair of eyeglasses in order to secure/release the device to/from the eyeglasses, multiple times. The clip-on device holds at least an inward-facing camera, a processor, a battery, and a wireless communication module. Most of the clip-on device may be located in front of the frame (as illustrated in FIG. 16b , FIG. 17b , and FIG. 20), or alternatively, most of the clip-on device may be located behind the frame, as illustrated in FIG. 18b and FIG. 19 b.

FIG. 16a , FIG. 16b , and FIG. 16c illustrate two right and left clip-on devices 141 and 142, respectively, configured to attached/detached from an eyeglasses frame 140. The clip-on device 142 includes an inward-facing head-mounted camera 143 pointed at a region on the lower part of the face (such as the upper lip, mouth, nose, and/or cheek), an inward-facing head-mounted camera 144 pointed at the forehead, and other electronics 145 (such as a processor, a battery, and/or a wireless communication module). The clip-on devices 141 and 142 may include additional cameras illustrated in the drawings as black circles.

FIG. 17a and FIG. 17b illustrate a clip-on device 147 that includes an inward-facing head-mounted camera 148 pointed at a region on the lower part of the face (such as the nose), and an inward-facing head-mounted camera 149 pointed at the forehead. The other electronics (such as a processor, a battery, and/or a wireless communication module) is located inside the box 150, which also holds the cameras 148 and 149.

FIG. 18a and FIG. 18b illustrate two right and left clip-on devices 160 and 161, respectively, configured to be attached behind an eyeglasses frame 165. The clip-on device 160 includes an inward-facing head-mounted camera 162 pointed at a region on the lower part of the face (such as the upper lip, mouth, nose, and/or cheek), an inward-facing head-mounted camera 163 pointed at the forehead, and other electronics 164 (such as a processor, a battery, and/or a wireless communication module). The clip-on devices 160 and 161 may include additional cameras illustrated in the drawings as black circles.

FIG. 19a and FIG. 19b illustrate a single-unit clip-on device 170, configured to be attached behind an eyeglasses frame 176. The single-unit clip-on device 170 includes inward-facing head-mounted cameras 171 and 172 pointed at regions on the lower part of the face (such as the upper lip, mouth, nose, and/or cheek), inward-facing head-mounted cameras 173 and 174 pointed at the forehead, a spring 175 configured to apply force that holds the clip-on device 170 to the frame 176, and other electronics 177 (such as a processor, a battery, and/or a wireless communication module). The clip-on device 170 may include additional cameras illustrated in the drawings as black circles.

FIG. 20 illustrates two right and left clip-on devices 153 and 154, respectively, configured to attached/detached from an eyeglasses frame, and having protruding arms to hold the inward-facing head-mounted cameras. Head-mounted camera 155 measures a region on the lower part of the face, head-mounted camera 156 measures regions on the forehead, and the left clip-on device 154 further includes other electronics 157 (such as a processor, a battery, and/or a wireless communication module). The clip-on devices 153 and 154 may include additional cameras illustrated in the drawings as black circles.

It is noted that the elliptic and other shapes of the ROIs in some of the drawings are just for illustration purposes, and the actual shapes of the ROIs are usually not as illustrated. It is possible to calculate the accurate shape of an ROI using various methods, such as a computerized simulation using a 3D model of the face and a model of a head-mounted system (HMS) to which a thermal camera is physically coupled, or by placing a LED instead of the sensor (while maintaining the same field of view) and observing the illumination pattern on the face. Furthermore, illustrations and discussions of a camera represent one or more cameras, where each camera may have the same FOV and/or different FOVs. Unless indicated to the contrary, the cameras may include one or more sensing elements (pixels), even when multiple sensing elements do not explicitly appear in the figures; when a camera includes multiple sensing elements then the illustrated ROI usually refers to the total ROI captured by the camera, which is made of multiple regions that are respectively captured by the different sensing elements. The positions of the cameras in the figures are just for illustration, and the cameras may be placed at other positions on the HMS.

Sentences in the form of an “ROI on an area”, such as ROI on the forehead or an ROI on the nose, refer to at least a portion of the area. Depending on the context, and especially when using a CAM having just one pixel or a small number of pixels, the ROI may cover another area (in addition to the area). For example, a sentence in the form of “an ROI on the nose” may refer to either: 100% of the ROI is on the nose, or some of the ROI is on the nose and some of the ROI is on the upper lip.

Various embodiments described herein involve detections of physiological responses based on user measurements. Some examples of physiological responses include stress, an allergic reaction, an asthma attack, a stroke, dehydration, intoxication, or a headache (which includes a migraine). Other examples of physiological responses include manifestations of fear, startle, sexual arousal, anxiety, joy, pain or guilt. Still other examples of physiological responses include physiological signals such as a heart rate or a value of a respiratory parameter of the user. Optionally, detecting a physiological response may involve one or more of the following: determining whether the user has/had the physiological response, identifying an imminent attack associated with the physiological response, and/or calculating the extent of the physiological response.

In some embodiments, detection of the physiological response is done by processing thermal measurements that fall within a certain window of time that characterizes the physiological response. For example, depending on the physiological response, the window may be five seconds long, thirty seconds long, two minutes long, five minutes long, fifteen minutes long, or one hour long. Detecting the physiological response may involve analysis of thermal measurements taken during multiple of the above-described windows, such as measurements taken during different days. In some embodiments, a computer may receive a stream of thermal measurements, taken while the user wears an HMS with coupled thermal cameras during the day, and periodically evaluate measurements that fall within a sliding window of a certain size.

In some embodiments, models are generated based on measurements taken over long periods. Sentences of the form of “measurements taken during different days” or “measurements taken over more than a week” are not limited to continuous measurements spanning the different days or over the week, respectively. For example, “measurements taken over more than a week” may be taken by eyeglasses equipped with thermal cameras, which are worn for more than a week, 8 hours a day. In this example, the user is not required to wear the eyeglasses while sleeping in order to take measurements over more than a week. Similarly, sentences of the form of “measurements taken over more than 5 days, at least 2 hours a day” refer to a set comprising at least 10 measurements taken over 5 different days, where at least two measurements are taken each day at times separated by at least two hours.

Utilizing measurements taken of a long period (e.g., measurements taken on “different days”) may have an advantage, in some embodiments, of contributing to the generalizability of a trained model. Measurements taken over the long period likely include measurements taken in different environments and/or measurements taken while the measured user was in various physiological and/or mental states (e.g., before/after meals and/or while the measured user was sleepy/energetic/happy/depressed, etc.). Training a model on such data can improve the performance of systems that utilize the model in the diverse settings often encountered in real-world use (as opposed to controlled laboratory-like settings). Additionally, taking the measurements over the long period may have the advantage of enabling collection of a large amount of training data that is required for some machine learning approaches (e.g., “deep learning”).

Detecting the physiological response may involve performing various types of calculations by a computer. Optionally, detecting the physiological response may involve performing one or more of the following operations: comparing thermal measurements to a threshold (when the threshold is reached that may be indicative of an occurrence of the physiological response), comparing thermal measurements to a reference time series, and/or by performing calculations that involve a model trained using machine learning methods. Optionally, the thermal measurements upon which the one or more operations are performed are taken during a window of time of a certain length, which may optionally depend on the type of physiological response being detected. In one example, the window may be shorter than one or more of the following durations: five seconds, fifteen seconds, one minute, five minutes, thirty minute, one hour, four hours, one day, or one week. In another example, the window may be longer than one or more of the aforementioned durations. Thus, when measurements are taken over a long period, such as measurements taken over a period of more than a week, detection of the physiological response at a certain time may be done based on a subset of the measurements that falls within a certain window near the certain time; the detection at the certain time does not necessarily involve utilizing all values collected throughout the long period.

In some embodiments, detecting the physiological response of a user may involve utilizing baseline thermal measurement values, most of which were taken when the user was not experiencing the physiological response. Optionally, detecting the physiological response may rely on observing a change to typical temperatures at one or more ROIs (the baseline), where different users might have different typical temperatures at the ROIs (i.e., different baselines). Optionally, detecting the physiological response may rely on observing a change to a baseline level, which is determined based on previous measurements taken during the preceding minutes and/or hours.

In some embodiments, detecting a physiological response involves determining the extent of the physiological response, which may be expressed in various ways that are indicative of the extent of the physiological response, such as: (i) a binary value indicative of whether the user experienced, and/or is experiencing, the physiological response, (ii) a numerical value indicative of the magnitude of the physiological response, (iii) a categorial value indicative of the severity/extent of the physiological response, (iv) an expected change in thermal measurements of an ROI (denoted TH_(ROI) or some variation thereof), and/or (v) rate of change in TH_(ROI). Optionally, when the physiological response corresponds to a physiological signal (e.g., a heart rate, a breathing rate, and an extent of frontal lobe brain activity), the extent of the physiological response may be interpreted as the value of the physiological signal.

One approach for detecting a physiological response, which may be utilized in some embodiments, involves comparing thermal measurements of one or more ROIs to a threshold. In these embodiments, the computer may detect the physiological response by comparing the thermal measurements, and/or values derived therefrom (e.g., a statistic of the measurements and/or a function of the measurements), to the threshold to determine whether it is reached. Optionally, the threshold may include a threshold in the time domain, a threshold in the frequency domain, an upper threshold, and/or a lower threshold. When a threshold involves a certain change to temperature, the certain change may be positive (increase in temperature) or negative (decrease in temperature). Different physiological responses described herein may involve different types of thresholds, which may be an upper threshold (where reaching the threshold means≥the threshold) or a lower threshold (where reaching the threshold means≤the threshold); for example, each physiological response may involve at least a certain degree of heating, or at least a certain degree cooling, at a certain ROI on the face.

Another approach for detecting a physiological response, which may be utilized in some embodiments, may be applicable when the thermal measurements of a user are treated as time series data. For example, the thermal measurements may include data indicative of temperatures at one or more ROIs at different points of time during a certain period. In some embodiments, the computer may compare thermal measurements (represented as a time series) to one or more reference time series that correspond to periods of time in which the physiological response occurred. Additionally or alternatively, the computer may compare the thermal measurements to other reference time series corresponding to times in which the physiological response did not occur. Optionally, if the similarity between the thermal measurements and a reference time series corresponding to a physiological response reaches a threshold, this is indicative of the fact that the thermal measurements correspond to a period of time during which the user had the physiological response. Optionally, if the similarity between the thermal measurements and a reference time series that does not correspond to a physiological response reaches another threshold, this is indicative of the fact that the thermal measurements correspond to a period of time in which the user did not have the physiological response. Time series analysis may involve various forms of processing involving segmenting data, aligning data, clustering, time warping, and various functions for determining similarity between sequences of time series data. Some of the techniques that may be utilized in various embodiments are described in Ding, Hui, et al. “Querying and mining of time series data: experimental comparison of representations and distance measures.” Proceedings of the VLDB Endowment 1.2 (2008): 1542-1552, and in Wang, Xiaoyue, et al. “Experimental comparison of representation methods and distance measures for time series data.” Data Mining and Knowledge Discovery 26.2 (2013): 275-309.

Herein, “machine learning” methods refers to learning from examples using one or more approaches. Optionally, the approaches may be considered supervised, semi-supervised, and/or unsupervised methods. Examples of machine learning approaches include: decision tree learning, association rule learning, regression models, nearest neighbors classifiers, artificial neural networks, deep learning, inductive logic programming, support vector machines, clustering, Bayesian networks, reinforcement learning, representation learning, similarity and metric learning, sparse dictionary learning, genetic algorithms, rule-based machine learning, and/or learning classifier systems.

Herein, a “machine learning-based model” is a model trained using machine learning methods. For brevity's sake, at times, a “machine learning-based model” may simply be called a “model”. Referring to a model as being “machine learning-based” is intended to indicate that the model is trained using machine learning methods (otherwise, “model” may also refer to a model generated by methods other than machine learning).

In some embodiments, which involve utilizing a machine learning-based model, a computer is configured to detect the physiological response by generating feature values based on the thermal measurements (and possibly other values), and/or based on values derived therefrom (e.g., statistics of the measurements). The computer then utilizes the machine learning-based model to calculate, based on the feature values, a value that is indicative of whether, and/or to what extent, the user is experiencing (and/or is about to experience) the physiological response. Optionally, calculating said value is considered “detecting the physiological response”. Optionally, the value calculated by the computer is indicative of the probability that the user has/had the physiological response.

Herein, feature values may be considered input to a computer that utilizes a model to perform the calculation of a value, such as the value indicative of the extent of the physiological response mentioned above. It is to be noted that the terms “feature” and “feature value” may be used interchangeably when the context of their use is clear. However, a “feature” typically refers to a certain type of value, and represents a property, while “feature value” is the value of the property with a certain instance (sample). For example, a feature may be temperature at a certain ROI, while the feature value corresponding to that feature may be 36.9° C. in one instance and 37.3° C. in another instance.

In some embodiments, a machine learning-based model used to detect a physiological response is trained based on data that includes samples. Each sample includes feature values and a label. The feature values may include various types of values. At least some of the feature values of a sample are generated based on measurements of a user taken during a certain period of time (e.g., thermal measurements taken during the certain period of time). Optionally, some of the feature values may be based on various other sources of information described herein. The label is indicative of a physiological response of the user corresponding to the certain period of time. Optionally, the label may be indicative of whether the physiological response occurred during the certain period and/or the extent of the physiological response during the certain period. Additionally or alternatively, the label may be indicative of how long the physiological response lasted. Labels of samples may be generated using various approaches, such as self-report by users, annotation by experts that analyze the training data, automatic annotation by a computer that analyzes the training data and/or analyzes additional data related to the training data, and/or utilizing additional sensors that provide data useful for generating the labels. It is to be noted that herein when it is stated that a model is trained based on certain measurements (e.g., “a model trained based on TH_(ROI) taken on different days”), it means that the model was trained on samples comprising feature values generated based on the certain measurements and labels corresponding to the certain measurements. Optionally, a label corresponding to a measurement is indicative of the physiological response at the time the measurement was taken.

Various types of feature values may be generated based on thermal measurements. In one example, some feature values are indicative of temperatures at certain ROIs. In another example, other feature values may represent a temperature change at certain ROIs. The temperature changes may be with respect to a certain time and/or with respect to a different ROI. In order to better detect physiological responses that take some time to manifest, in some embodiments, some feature values may describe temperatures (or temperature changes) at a certain ROI at different points of time. Optionally, these feature values may include various functions and/or statistics of the thermal measurements such as minimum/maximum measurement values and/or average values during certain windows of time.

It is to be noted that when it is stated that feature values are generated based on data comprising multiple sources, it means that for each source, there is at least one feature value that is generated based on that source (and possibly other data). For example, stating that feature values are generated from thermal measurements of first and second ROIs (TH_(ROI1) and TH_(ROI2), respectively) means that the feature values may include a first feature value generated based on TH_(ROI1) and a second feature value generated based on TH_(ROI2). Optionally, a sample is considered generated based on measurements of a user (e.g., measurements comprising TH_(ROI1) and TH_(ROI2)) when it includes feature values generated based on the measurements of the user.

In addition to feature values that are generated based on thermal measurements, in some embodiments, at least some feature values utilized by a computer (e.g., to detect a physiological response or train a mode) may be generated based on additional sources of data that may affect temperatures measured at various facial ROIs. Some examples of the additional sources include: (i) measurements of the environment such as temperature, humidity level, noise level, elevation, air quality, a wind speed, precipitation, and infrared radiation; (ii) contextual information such as the time of day (e.g., to account for effects of the circadian rhythm), day of month (e.g., to account for effects of the lunar rhythm), day in the year (e.g., to account for seasonal effects), and/or stage in a menstrual cycle; (iii) information about the user being measured such as sex, age, weight, height, and/or body build. Alternatively or additionally, at least some feature values may be generated based on physiological signals of the user obtained by sensors that are not thermal cameras, such as a visible-light camera, a photoplethysmogram (PPG) sensor, an electrocardiogram (ECG) sensor, an electroencephalography (EEG) sensor, a galvanic skin response (GSR) sensor, or a thermistor.

The machine learning-based model used to detect a physiological response may be trained, in some embodiments, based on data collected in day-to-day, real world scenarios. As such, the data may be collected at different times of the day, while users perform various activities, and in various environmental conditions. Utilizing such diverse training data may enable a trained model to be more resilient to the various effects different conditions can have on the values of thermal measurements, and consequently, be able to achieve better detection of the physiological response in real world day-to-day scenarios.

Since real world day-to-day conditions are not the same all the time, sometimes detection of the physiological response may be hampered by what is referred to herein as “confounding factors”. A confounding factor can be a cause of warming and/or cooling of certain regions of the face, which is unrelated to a physiological response being detected, and as such, may reduce the accuracy of the detection of the physiological response. Some examples of confounding factors include: (i) environmental phenomena such as direct sunlight, air conditioning, and/or wind; (ii) things that are on the user's face, which are not typically there and/or do not characterize the faces of most users (e.g., cosmetics, ointments, sweat, hair, facial hair, skin blemishes, acne, inflammation, piercings, body paint, and food leftovers); (iii) physical activity that may affect the user's heart rate, blood circulation, and/or blood distribution (e.g., walking, running, jumping, and/or bending over); (iv) consumption of substances to which the body has a physiological response that may involve changes to temperatures at various facial ROIs, such as various medications, alcohol, caffeine, tobacco, and/or certain types of food; and/or (v) disruptive facial movements (e.g., frowning, talking, eating, drinking, sneezing, and coughing).

Occurrences of confounding factors may not always be easily identified in thermal measurements. Thus, in some embodiments, systems may incorporate measures designed to accommodate for the confounding factors. In some embodiments, these measures may involve generating feature values that are based on additional sensors, other than the thermal cameras. In some embodiments, these measures may involve refraining from detecting the physiological response, which should be interpreted as refraining from providing an indication that the user has the physiological response. For example, if an occurrence of a certain confounding factor is identified, such as strong directional sunlight that heats one side of the face, the system may refrain from detecting that the user had a stroke. In this example, the user may not be alerted even though a temperature difference between symmetric ROIs on both sides of the face reaches a threshold that, under other circumstances, would warrant alerting the user.

Training data used to train a model for detecting a physiological response may include, in some embodiments, a diverse set of samples corresponding to various conditions, some of which involve occurrence of confounding factors (when there is no physiological response and/or when there is a physiological response). Having samples in which a confounding factor occurs (e.g., the user is in direct sunlight or touches the face) can lead to a model that is less susceptible to wrongfully detect the physiological response (which may be considered an occurrence of a false positive) in real world situations.

When a model is trained with training data comprising samples generated from measurements of multiple users, the model may be considered a general model. When a model is trained with training data comprising at least a certain proportion of samples generated from measurements of a certain user, and/or when the samples generated from the measurements of the certain user are associated with at least a certain proportion of weight in the training data, the model may be considered a personalized model for the certain user. Optionally, the personalized model for the certain user provides better results for the certain user, compared to a general model that was not personalized for the certain user. Optionally, personalized model may be trained based on measurements of the certain user, which were taken while the certain user was in different situations; for example, train the model based on measurements taken while the certain user had a headache/epilepsy/stress/anger attack, and while the certain user did not have said attack. Additionally or alternatively, the personalized model may be trained based on measurements of the certain user, which were taken over a duration long enough to span different situations; examples of such long enough durations may include: a week, a month, six months, a year, and three years.

Training a model that is personalized for a certain user may require collecting a sufficient number of training samples that are generated based on measurements of the certain user. Thus, initially detecting the physiological response with the certain user may be done utilizing a general model, which may be replaced by a personalized model for the certain user, as a sufficiently large number of samples are generated based on measurements of the certain user. Another approach involves gradually modifying a general model based on samples of the certain user in order to obtain the personalized model.

After a model is trained, the model may be provided for use by a system that detects the physiological response. Providing the model may involve performing different operations. In one embodiment, providing the model to the system involves forwarding the model to the system via a computer network and/or a shared computer storage medium (e.g., writing the model to a memory that may be accessed by the system that detects the physiological response). In another embodiment, providing the model to the system involves storing the model in a location from which the system can retrieve the model, such as a database and/or cloud-based storage from which the system may retrieve the model. In still another embodiment, providing the model involves notifying the system regarding the existence of the model and/or regarding an update to the model. Optionally, this notification includes information needed in order for the system to obtain the model.

A model for detecting a physiological response may include different types of parameters. Following are some examples of various possibilities for the model and the type of calculations that may be accordingly performed by a computer in order to detect the physiological response: (a) the model comprises parameters of a decision tree. Optionally, the computer simulates a traversal along a path in the decision tree, determining which branches to take based on the feature values. A value indicative of the physiological response may be obtained at the leaf node and/or based on calculations involving values on nodes and/or edges along the path; (b) the model comprises parameters of a regression model (e.g., regression coefficients in a linear regression model or a logistic regression model). Optionally, the computer multiplies the feature values (which may be considered a regressor) with the parameters of the regression model in order to obtain the value indicative of the physiological response; and/or (c) the model comprises parameters of a neural network. For example, the parameters may include values defining at least the following: (i) an interconnection pattern between different layers of neurons, (ii) weights of the interconnections, and (iii) activation functions that convert each neuron's weighted input to its output activation. Optionally, the computer provides the feature values as inputs to the neural network, computes the values of the various activation functions and propagates values between layers, and obtains an output from the network, which is the value indicative of the physiological response.

A user interface (UI) may be utilized, in some embodiments, to notify the user and/or some other entity, such as a caregiver, about the physiological response and/or present an alert responsive to an indication that the extent of the physiological response reaches a threshold. The UI may include a screen to display the notification and/or alert, a speaker to play an audio notification, a tactile UI, and/or a vibrating UI. In some embodiments, “alerting” about a physiological response of a user refers to informing about one or more of the following: the occurrence of a physiological response that the user does not usually have (e.g., a stroke, intoxication, and/or dehydration), an imminent physiological response (e.g., an allergic reaction, an epilepsy attack, and/or a migraine), and an extent of the physiological response reaching a threshold (e.g., stress and/or anger reaching a predetermined level).

FIG. 21 illustrates a scenario in which an alert regarding a possible stroke is issued. The figure illustrates a user wearing a frame with at least two CAMs (562 and 563) for measuring ROIs on the right and left cheeks (ROIs 560 and 561, respectively). The measurements indicate that the left side of the face is colder than the right side of the face. Based on these measurements, and possibly additional data, the system detects the stroke and issues an alert. Optionally, the user's facial expression is slightly distorted and asymmetric, and a VCAM provides additional data in the form of images that may help detecting the stroke.

The CAMs can take respiratory-related thermal measurements when their ROIs are on the user's upper lip, the user's mouth, the space where the exhale stream form the user's nose flows, and/or the space where the exhale stream from the user's mouth flows. In some embodiments, one or more of the following respiratory parameters may be calculated based on the respiratory-related thermal measurements taken during a certain period of time:

“Breathing rate” represents the number of breaths per minute the user took during the certain period. The breathing rate may also be formulated as the average time between successive inhales and/or the average between successive exhales.

“Respiration volume” represents the volume of air breathed over a certain duration (usually per minute), the volume of air breathed during a certain breath, tidal volume, and/or the ratio between two or more breaths. For example, the respiration volume may indicate that a first breath was deeper than a second breath, or that breaths during a first minute were shallower than breaths during a second minute.

“Mouth breathing vs nasal breathing” indicates whether during the certain period the user breathed mainly through the mouth (a state characterized as “mouth breathing”) or mainly through the nose (a state characterized as “nose breathing” or “nasal breathing”). Optionally, this parameter may represent the ratio between nasal and mouth breathing, such as a proportion of the certain period during which the breathing was more mouth breathing, and/or the relative volume of air exhaled through the nose vs the mouth. In one example, breathing mainly through the mouth refers to inhaling more than 50% of the air through the mouth (and less than 50% of the air through the nose).

“Exhale duration/Inhale duration” represents the exhale(s) duration during the certain period, the inhale(s) duration during the certain period, and/or a ratio of the two aforementioned durations. Optionally, this respiratory parameter may represent one or more of the following: (i) the average duration of the exhales and/or inhales, (ii) a maximum and/or minimum duration of the exhales and/or inhales during the certain period, and (iii) a proportion of times in which the duration of exhaling and/or inhaling reached a certain threshold.

“Post-exhale breathing pause” represents the time that elapses between when the user finishes exhaling and starts inhaling again. “Post-inhale breathing pause” represents the time that elapses between when the user finishes inhaling and when the user starts exhaling after that. The post exhale/inhale breathing pauses may be formulated utilizing various statistics, such as an average post exhale/inhale breathing pause during a certain period, a maximum or minimum duration of post exhale/inhale breathing pause during the certain period, and/or a proportion of times in which the duration of post exhale/inhale breathing pause reached a certain threshold.

“Dominant nostril” is the nostril through which most of the air is exhaled (when exhaling through the nose). Normally the dominant nostril changes during the day, and the exhale is considered balanced when the amount of air exhaled through each nostril is similar. Optionally, the breathing may be considered balanced when the difference between the volumes of air exhaled through the right and left nostrils is below a predetermined threshold, such as 20% or 10%. Additionally or alternatively, the breathing may be considered balanced during a certain duration around the middle of the switching from right to left or left to right nostril dominance. For example, the certain duration of balanced breathing may be about 4 minutes at the middle of the switching between dominant nostrils.

“Temperature of the exhale stream” may be measured based on thermal measurements of the stream that flows from one or both nostrils, and/or the heat pattern generated on the upper lip by the exhale stream from the nose. In one example, it is not necessary to measure the exact temperature of the exhale stream as long as the system is able to differentiate between different temperatures of the exhale stream based on the differences between series of thermal measurements taken at different times. Optionally, the series of thermal measurements that are compared are temperature measurements received from the same pixel(s) of a head-mounted thermal camera.

“Shape of the exhale stream” (also referred to as “SHAPE”) represents the three-dimensional (3D) shape of the exhale stream from at least one of the nostrils. The SHAPE changes during the day and may reflect the mental, physiological, and/or energetic state of a user. Usually the temperature of the exhale stream is different from the temperature of the air in the environment; this enables a thermal camera, which captures a portion of the volume through which the exhale stream flows, to take a measurement indicative of the SHAPE, and/or to differentiate between different shapes of the exhale stream (SHAPEs). Additionally, the temperature of the exhale stream is usually different from the temperature of the upper lip, and thus exhale streams having different shapes may generate different thermal patterns on the upper lip. Measuring these different thermal patterns on the upper lip may enable a computer to differentiate between different SHAPEs. In one embodiment, differences between values measured by adjacent thermal pixels of CAM, which measure the exhale stream and/or the upper lip over different time intervals, may correspond to different SHAPEs. In one example, it is not necessary to measure the exact SHAPE as long as it is possible to differentiate between different SHAPEs based on the differences between the values of the adjacent thermal pixels. In another embodiment, differences between average values, measured by the same thermal pixel over different time intervals, may correspond to different SHAPEs. In still another embodiment, the air that is within certain boundaries of a 3D shape that protrudes from the user's nose, which is warmer than the environment air, as measured by CAM, is considered to belong to the exhale stream.

In one embodiment, the SHAPE may be represented by one or more thermal images taken by one or more CAMs. In this embodiment, the shape may correspond to a certain pattern in the one or more images and/or a time series describing a changing pattern in multiple images. In another embodiment, the SHAPE may be represented by at least one of the following parameters: the angle from which the exhale stream blows from a nostril, the width of the exhale stream, the length of the exhale stream, and other parameters that are indicative of the 3D SHAPE. Optionally, the SHAPE may be defined by the shape of a geometric body that confines it, such as a cone or a cylinder, protruding from the user's nose. For example, the SHAPE may be represented by parameters such as the cone's height, the radius of the cone's base, and/or the angle between the cone's altitude axis and the nostril.

“Smoothness of the exhale stream” represents a level of smoothness of the exhale stream from the nose and/or the mouth. In one embodiment, the smoothness of the exhale stream is a value that can be determined based on observing the smoothness of a graph of the respiratory-related thermal measurements. Optionally, it is unnecessary for the system to measure the exact smoothness of the exhale stream as long as it is able to differentiate between smoothness levels of respiratory-related thermal measurements taken at different times. Optionally, the compared thermal measurements taken at different times may be measured by the same pixels and/or by different pixels. As a rule of thumb, the smoother the exhale stream, the lower the stress and the better the physical condition. For example, the exhale stream of a healthy young person is often smoother than the exhale stream of an elderly person, who may even experience short pauses in the act of exhaling.

There are well known mathematical methods to calculate the smoothness of a graph, such as Fourier transform analysis, polynomial fit, differentiability classes, multivariate differentiability classes, parametric continuity, and/or geometric continuity. In one example, the smoothness of TH_(ROI) indicative of the exhale stream is calculated based on a Fourier transform of a series of TH_(ROI). In the case of Fourier transform, the smaller the power of the high-frequencies portion, the smoother the exhale is, and vice versa. Optionally, one or more predetermined thresholds differentiate between the high-frequency and low-frequency portions in the frequency domain. In another example, the smoothness of TH_(ROI) indicative of the exhale stream is calculated using a polynomial fit (with a bounded degree) of a series of TH_(ROI). Optionally, the degree of the polynomial used for the fit is proportional (e.g., linear) to the number of exhales in the time series. In the case of polynomial fit, the smoothness may be a measure of the goodness of fit between the series of TH_(ROI) and the polynomial. For example, the lower the squared error, the smoother the graph is considered. In still another embodiment, the smoothness of TH_(ROI) indicative of the exhale stream may be calculated using a machine learning-based model trained with training data comprising reference time series of TH_(ROI) for which the extent of smoothness is known.

In an alternative embodiment, a microphone is used to measure the exhale sounds. The smoothness of the exhale stream may be a value that is proportional to the smoothness of the audio measurement time series taken by the microphone (e.g., as determined based on the power of the high-frequency portion obtained in a Fourier transform of the time series of the audio).

There are various approaches that may be employed in order to calculate values of one or more of the respiratory parameters mentioned above based on respiratory-related thermal measurements. Optionally, calculating the values of one or more of the respiratory parameters may be based on additional inputs, such as statistics about the user (e.g., age, gender, weight, height, and the like), indications about the user's activity level (e.g., input from a pedometer), and/or physiological signals of the user (e.g., heart rate and respiratory rate). Roughly speaking, some approaches may be considered analytical approaches, while other approaches may involve utilization of a machine learning-based model.

In some embodiments, one or more of the respiratory parameters mentioned above may be calculated based on the respiratory-related thermal measurements by observing differences in thermal measurements. In one embodiment, certain pixels that have alternating temperature changes may be identified as corresponding to exhale streams. In this embodiment, the breathing rate may be a calculated frequency of the alternating temperature changes at the certain pixels. In another embodiment, the relative difference in magnitude of temperature changes at different ROIs, such as the alternating temperature changes that correspond to breathing activity, may be used to characterize different types of breathing. For example, if temperature changes at ROI near the nostrils reach a first threshold, while temperature changes at an ROI related to the mouth do not reach a second threshold, then the breathing may be considered nasal breathing; while if the opposite occurs, the breathing may be considered mouth breathing. In another example, if temperature changes at an ROI near the left nostril and/or on the left side of the upper lip are higher than temperature changes at an ROI near the right nostril and/or on the right side of the upper lip, then the left nostril may be considered the dominant nostril at the time the measurements were taken. In still another example, the value of a respiratory parameter may be calculated as a function of one or more input values from among the respiratory-related thermal measurements.

In other embodiments, one or more of the respiratory parameters may be calculated by generating feature values based on the respiratory-related thermal measurements and utilizing a model to calculate, based on the feature values, the value of a certain respiratory parameter from among the parameters mentioned above. The model for the certain respiratory parameter is trained based on samples. Each sample comprises the feature values based on respiratory-related thermal measurements, taken during a certain period of time, and a label indicative of the value of the certain respiratory parameter during the certain period of time. For example, the feature values generated for a sample may include the values of pixels measured by the one or more cameras, statistics of the values of the pixels, and/or functions of differences of values of pixels at different times. Additionally or alternatively, some of the feature values may include various low-level image analysis features, such as feature derived using Gabor filters, local binary patterns and their derivatives, features derived using algorithms such as SIFT, SURF, and/or ORB, image keypoints, HOG descriptors and features derived using PCA or LDA. The labels of the samples may be obtained through various ways. Some examples of approaches for generating the labels include manual reporting (e.g., a user notes the type of his/her breathing), manual analysis of thermal images (e.g., an expert determines a shape of an exhale stream), and/or utilizing sensors (e.g., a chest strap that measures the breathing rate and volume).

Training the model for the certain respiratory parameter based on the samples may involve utilizing one or more machine learning-based training algorithms, such as a training algorithm for a decision tree, a regression model, or a neural network. Once the model is trained, it may be utilized to calculate the value of the certain respiratory parameter based on feature values generated based on respiratory-related thermal measurements taken during a certain period, for which the label (i.e., the value of the certain respiratory parameter) may not be known.

In one embodiment, a system configured to calculate a respiratory parameter includes an inward-facing head-mounted thermal camera (CAM) and a computer. CAM is worn on a user's head and takes thermal measurements of a region below the nostrils (TH_(ROI)), where TH_(ROI) are indicative of the exhale stream. The “region below the nostrils”, which is indicative of the exhale stream, refers to one or more regions on the upper lip, the mouth, and/or air volume(s) through which the exhale streams from the nose and/or mouth flow. The flowing of the typically warm air of the exhale stream can change the temperature at the one or more regions, and thus thermal measurements of these one or more regions can provide information about properties of the exhale stream. The computer (i) generates feature values based on TH_(ROI), and (ii) utilizes a model to calculate the respiratory parameter based on the feature values. The respiratory parameter may be indicative of the user's breathing rate, and the model may be trained based on previous TH_(ROI) of the user taken during different days. FIG. 36b illustrates one embodiment of a system for calculating a respiratory parameter. The system includes a computer 445 and CAM that is coupled to the eyeglasses frame worn by the user 420 and provides TH_(ROI) 443.

The computer 445 generates feature values based on TH_(ROI) 443, and possibly other sources of data. Then the computer utilizes a model 442 to calculate, based on the feature values, a value 447 of the respiratory parameter. The value 447 may be indicative of at least one of the following: breathing rate, respiration volume, whether the user is breathing mainly through the mouth or through the nose, exhale (inhale) duration, post-exhale (post-inhale) breathing pause, a dominant nostril, a shape of the exhale stream, smoothness of the exhale stream, and/or temperature of the exhale stream. Optionally, the respiratory parameters calculated by the computer 445 may be indicative of the respiration volume. Optionally, the value 447 is stored (e.g., for life-logging purposes) and/or forwarded to a software agent operating on behalf of the user (e.g., in order for the software agent to make a decision regarding the user).

The feature values generated by the computer 445 may include any of the feature values described in this disclosure that are utilized to detect a physiological response. Optionally, the thermal measurements may undergo various forms of filtering and/or normalization. For example, the feature values generated based on TH_(ROI) may include: time series data comprising values measured by CAM, average values of certain pixels of CAM, and/or values measured at certain times by the certain pixels. Additionally, the feature values may include values generated based on additional measurements of the user taken by one or more additional sensors (e.g., measurements of heart rate, heart rate variability, brainwave activity, galvanic skin response, muscle activity, and/or an extent of movement). Additionally or alternatively, at least some of the feature values may include measurements of the environment in which the user is in, and/or confounding factors that may interfere with the detection.

A user interface (UI) 448 may be utilized to present the value 447 of the respiratory parameter and/or present an alert (e.g., to the user 420 and/or to a caregiver). In one example, UI 448 may be used to alert responsive to an indication that the value 447 reaches a threshold (e.g., when the breathing rate exceeds a certain value and/or after the user 420 spent a certain duration mouth breathing instead of nasal breathing). In another example, UI 448 may be used to alert responsive to detecting that the probability of a respiratory-related attack reaches a threshold.

In one embodiment, the value 447 may be indicative of the smoothness of the exhale stream. Optionally, the value 447 may be presented to the user 420 to increase the user's awareness to the smoothness of his/her exhale stream. Optionally, responsive to detecting that the smoothness is below a predetermined threshold, the computer 445 may issue an alert for the user 420 (e.g., via the UI 448) in order to increase the user's awareness to the user's breathing.

The model 442 is trained on data that includes previous TH_(ROI) of the user 420 and possibly other users. Optionally, the previous measurements were taken on different days and/or over a period longer than a week. Training the model 442 typically involves generating samples based on the previous TH_(ROI) and corresponding labels indicative of values of the respiratory parameter. The labels may come from different sources. In one embodiment, one or more of the labels may be generated using a sensor that is not a thermal camera, which may or may not be physically coupled to a frame worn by the user. The sensor's measurements may be analyzed by a human expert and/or a software program in order to generate the labels. In one example, the sensor is part of a smart shirt and/or chest strap that measures various respiratory (and other) parameters, such as Hexoskin™ smart shirt. In another embodiment, one or more of the labels may come from an external source such as an entity that observes the user, which may be a human observer or a software program. In yet another embodiment, one or more of the labels may be provided by the user, for example by indicating whether he/she is breathing through the mouth or nose and/or which nostril is dominant.

The samples used to train the model 442 usually include samples corresponding to different values of the respiratory parameter. In some embodiments, the samples used to train the model 442 include samples generated based on TH_(ROI) taken at different times of the day, while being at different locations, and/or while conducting different activities. In one example, the samples are generated based on TH_(ROI) taken in the morning and TH_(ROI) taken in the evening. In another example, the samples are generated based on TH_(ROI) of a user taken while being indoors, and TH_(ROI) of the user taken while being outdoors. In yet another example, the samples are generated based on TH_(ROI) taken while a user was sitting down, and TH_(ROI) taken while the user was walking, running, and/or engaging in physical exercise (e.g., dancing, biking, etc.).

Additionally or alternatively, the samples used to train the model 442 may be generated based on TH_(ROI) taken while various environmental conditions persisted. For example, the samples include first and second samples generated based on TH_(ROI) taken while the environment had first and second temperatures, with the first temperature being at least 10° C. warmer than the second temperature. In another example, the samples include samples generated based on measurements taken while there were different extents of direct sunlight and/or different extents of wind blowing.

Various computational approaches may be utilized to train the model 442 based on the samples described above. In one example, training the model 442 may involve selecting a threshold based on the samples. Optionally, if a certain feature value reaches the threshold then a certain respiratory condition is detected (e.g., unsmooth breathing). Optionally, the model 442 includes a value describing the threshold. In another example, a machine learning-based training algorithm may be utilized to train the model 442 based on the samples. Optionally, the model 442 includes parameters of at least one of the following types of models: a regression model, a neural network, a nearest neighbor model, a support vector machine, a support vector machine for regression, a naïve Bayes model, a Bayes network, and a decision tree.

In some embodiments, a deep learning algorithm may be used to train the model 442. In one example, the model 442 may include parameters describing multiple hidden layers of a neural network. In one embodiment, when TH_(ROI) include measurements of multiple pixels, the model 442 may include a convolution neural network (CNN). In one example, the CNN may be utilized to identify certain patterns in the thermal images, such as patterns of temperatures in the region of the exhale stream that may be indicative of a respiratory parameter, which involve aspects such as the location, direction, size, and/or shape of an exhale stream from the nose and/or mouth. In another example, calculating a value of a respiratory parameter, such as the breathing rate, may be done based on multiple, possibly successive, thermal measurements. Optionally, calculating values of the respiratory parameter based on thermal measurements may involve retaining state information that is based on previous measurements. Optionally, the model 442 may include parameters that describe an architecture that supports such a capability. In one example, the model 442 may include parameters of a recurrent neural network (RNN), which is a connectionist model that captures the dynamics of sequences of samples via cycles in the network's nodes. This enables RNNs to retain a state that can represent information from an arbitrarily long context window. In one example, the RNN may be implemented using a long short-term memory (LSTM) architecture. In another example, the RNN may be implemented using bidirectional recurrent neural network architecture (BRNN).

The computer 445 may detect a respiratory-related attack (such as an asthma attack, an epileptic attack, an anxiety attack, a panic attack, and a tantrum) based on feature values generated based on TH_(ROI) 443. The computer 445 may further receive additional inputs (such as indications of consuming a substance, a situation of the user, and/or thermal measurements of the forehead), and detect the respiratory-related attack based on the additional inputs. For example, the computer 445 may generate one or more of the feature values used to calculate the value 447 based on the additional inputs.

In a first embodiment, the computer 445 utilizes an indication of consumption of a substance to detect a respiratory-related attack. Optionally, the model 442 is trained based on: a first set of TH_(ROI) taken while the user experienced a respiratory-related attack after consuming the substance, and a second set of TH_(ROI) taken while the user did not experience a respiratory-related attack after consuming the substance. The duration to which “after consuming” refers depends on the substance and may last from minutes to hours. Optionally, the consuming of the substance involves consuming a certain drug and/or consuming a certain food item, and the indication is indicative of the time and/or the amount consumed.

In a second embodiment, the computer 445 utilizes an indication of a situation of the user to detect a respiratory-related attack. Optionally, the model 442 is trained based on: a first set of TH_(ROI) taken while the user was in the situation and experienced a respiratory-related attack, and a second set of TH_(ROI) taken while the user was in the situation and did not experience a respiratory-related attack. Optionally, the situation involves (i) interacting with a certain person, (ii) a type of activity the user is conducting, selected from at least two different types of activities associated with different levels of stress, and/or (iii) a type of activity the user is about to conduct (e.g., within thirty minutes), selected from at least two different types of activities associated with different levels of stress.

In a third embodiment, the system includes another CAM that takes thermal measurements of a region on the forehead (TH_(F)) of the user, and the computer 445 detects a respiratory related attack based on TH_(ROI) and TH_(F). For example, TH_(ROI) and TH_(F) may be utilized to generate one or more of the feature values used to calculate the value indicative of the probability that the user is experiencing, or is about to experience, the respiratory-related attack. Optionally, the model 442 was trained based on a first set of TH_(ROI) and TH_(F) taken while the user experienced a respiratory-related attack, and a second set of TH_(ROI) and TH_(F) taken while the user did not experience a respiratory-related attack.

The system may optionally include a sensor 435 that takes measurements m_(move) 450 that are indicative of movements of the user 420; the system further detects the physiological response based on m_(move) 450. The sensor 435 may include one or more of the following sensors: a gyroscope and/or an accelerometer, an outward-facing visible-light camera (that feeds an image processing algorithm to detect movement from a series of images), a miniature radar (such as low-power radar operating in the range between 30 GHz and 3,000 GHz), a miniature active electro-optics distance measurement device (such as a miniature Lidar), and/or a triangulation wireless device (such as a GPS receiver). Optionally, the sensor 435 is physically coupled to the frame or belongs to a device carried by the user (e.g., a smartphone or a smartwatch).

In a first embodiment, the computer 445 may detect the respiratory-related attack if the value 447 of the respiratory parameter reaches a first threshold, while m_(move) 450 do not reach a second threshold. In one example, reaching the first threshold indicates a high breathing rate, which may be considered too high for the user. Additionally, in this example, reaching the second threshold may mean that the user is conducting arduous physical activity. Thus, if the user is breathing too fast and this is not because of physical activity, then the computer 445 detects this as an occurrence of a respiratory-related attack (e.g., an asthma attack or a panic attack).

In a second embodiment, the computer 445 may generate feature values based on m_(move) 450 in addition to TH_(ROI) 443, and utilize an extended model to calculate, based on these feature values, a value indicative of the probability that the user is experiencing, or is about to experience, the respiratory related attack. In one example, the feature values used along with the extended model (which may be the model 442 or another model) include one or more of the following: (i) values comprised in TH_(ROI) 443, (ii) values of a respiratory parameter of the user 420, which are generated based on TH_(ROI) 443 (iii) values generated based on additional measurements of the user 420 (e.g., measurements of heart rate, heart rate variability, brainwave activity, galvanic skin response, muscle activity, and an extent of movement), (iv) measurements of the environment in which the user 420 was in while TH_(ROI) 443 were taken, (v) indications of various occurrences which may be considered confounding factors (e.g., touching the face, thermal radiation directed at the face, or airflow directed at the face), and/or (vi) values indicative of movements of the user (which are based on m_(move) 450).

The extended model is trained on samples generated from prior m_(move) and TH_(ROI), and corresponding labels indicating times of having the respiratory-related attack. The labels may come from various sources, such as measurements of the user (e.g., to detect respiratory distress), observations by a human and/or software, and/or the indications may be self-reported by the user. The samples used to train the extended model may be generated based on measurements taken over different days, and encompass measurements taken when the user was in different situations.

Usually the exhaled air warms up the skin below the nostrils, and during inhale the skin below the nostrils cools. This enables the system to identify the exhale based on measuring an increase in the temperature of the skin below the nostrils an inhale, and identify the inhale based on measuring a decrease in the temperature of the skin below the nostrils.

Synchronizing a physical effort with the breathing is highly recommended by therapists and sport instructors. For example, some elderly and/or unfit people can find it difficult to stand up and/or make other physical efforts because many of them do not exhale while making the effort, and/or do not synchronize the physical effort with their breathing. These people can benefit from a system that reminds them to exhale while making the effort, and/or helps them synchronize the physical effort with their breathing. As another example, in many kinds of physical activities it is highly recommended to exhale while making a physical effort and/or exhale during certain movements (such as exhale while bending down in Uttanasana).

In one embodiment, the computer 445 determines based on m_(move) 450 and TH_(ROI) 443 whether the user exhaled while making a physical effort above a predetermined threshold. Optionally, the computer receives a first indication that the user is making or is about to make the physical effort, commands a user interface (UI) to suggest the user to exhale while making the physical effort, and commands the UI to play a positive feedback in response to determining that the user managed to exhale while making the physical effort. Additionally, the computer may further command the UI to play an explanation why the user should try next time to exhale while making the physical effort in response to determining that the user did not exhale while making the physical effort.

FIG. 26a to FIG. 27c illustrate how the system described above may help train an elderly user to exhale during effort. In FIG. 26a the system identifies that the user inhaled rather than exhaled while getting up from a sitting position in a chair; the system alerts the user about this finding and suggests that next time the user should exhale while getting up. In FIG. 26b , the system identifies that the user exhaled at the correct time and commends the user on doing so. Examples of physical efforts include standing up, sitting down, manipulating with the hands an item that requires applying a significant force, defecating, dressing, leaning over, and/or lifting an item.

In FIG. 27a the system identifies that the user inhaled rather than exhaled while bending down to the dishwasher, and presents a thumbs-down signal (e.g., on the user's smartphone). In FIG. 27b the system identifies that the user exhaled while bending down to the dishwasher, and presents a thumbs-up signal. In FIG. 27c illustrates a smartphone app for counting the thumbs-up and thumbs-down signals identified during a day. The app may show various statistics, such as thumbs-up/thumbs-down during the past week, from start training with the app, according to locations the user is, while being with certain people, and/or organized according to types of exercises (such as a first counter for yoga, a second counter for housework, and a third counter for breathing during work time).

In one embodiment, the computer 445: (i) receives from a fitness app (also known as a personal trainer app) an indication that the user should exhale while making a movement, (ii) determines, based on m_(move), when the user is making the movement, and (iii) determines, based on TH_(ROI), whether the user exhaled while making the movement. Optionally, the computer commands the UI to (i) play a positive feedback in response to determining that the user managed to exhale while making the physical effort, and/or (ii) play an alert and/or an explanation why the user should try next time to exhale while making the physical effort in response to determining that the user did not exhale while making the physical effort. FIG. 28a illustrates a fitness app running on smartphone 196, which instructs the user to exhale while bending down. CAM coupled to eyeglasses frame 181 measures the user breathing and is utilized by the fitness app that helps the user to exhale correctly. FIG. 28b illustrates instructing the user to inhale while straightening up.

In another embodiment, the computer 445: (i) receives from a fitness app a certain number of breath cycles during which the user should perform a physical exercise, such as keeping a static yoga pose for a certain number of breath cycles, or riding a spin bike at a certain speed for a certain number of breath cycles, (ii) determines, based on m_(move), when the user performs the physical exercise, and (iii) counts, based on TH_(ROI), the number of breath cycles the user had while performing the physical exercise. Optionally, the computer commands the UI to play an instruction switch to another physical exercise responsive to detecting that the user performed the physical exercise for the certain number of breath cycles. Additionally or alternatively, the computer commands the UI to play a feedback that refers to the number of counted breath cycles responsive to detecting that the user performed the physical exercise for a number of breath cycles that is lower than the certain number of breath cycles. FIG. 29 illustrates a fitness app running on smartphone 197, which instructs the user to stay in a triangle pose for 8 breath cycles. CAM coupled to eyeglasses frame 181 measures the breathing and is utilized by the fitness app that calculates the breath cycles and counts the time to stay in the triangle pose according to the measured breath cycles.

The duration of exhaling and inhaling (denoted herein t_(exhale) and t_(inhale), respectively) can have various physiological effects. For example, for some users, breathing with prolonged inhales (relative to the exhales) can increase the possibility of suffering an asthma attack. In particular, keeping the duration of exhaling longer than the duration of inhaling (i.e., t_(exhale)/t_(inhale)>1, and preferably t_(exhale)/t_(inhale)≥2) may provide many benefits, such as having a calming effect and relieving asthma symptoms. In one embodiment, a computer is further configured to calculate, based on TH_(ROI), the ratio between exhale and inhale durations (t_(exhale)/t_(inhale)).

Many people are not aware of their breathing most of the time. These people can benefit from a system that is able to calculate t_(exhale)/t_(inhale) and provide them with feedback when it is beneficial to increase the ratio. In one embodiment, a computer suggests the user, via the UI, to increase t_(exhale)/t_(inhale) when it falls below a threshold. Optionally, the computer updates occasionally the calculation of t_(exhale)/t_(inhale), and suggests to progressively increase t_(exhale)/t_(inhale) at least until reaching a ratio of 1.5. Optionally, the computer stops suggesting to the user to increase t_(exhale)/t_(inhale) responsive to identifying that t_(exhale)/t_(inhale)≥2. In another embodiment, the computer is configured to: (i) receive a first indication that the user's stress level reaches a first threshold, (ii) identify, based on TH_(ROI), that the ratio between exhaling and inhaling durations (t_(exhale)/t_(inhale)) is below a second threshold that is below 1.5, and (iii) command the UI to suggest to the user to prolong the exhale until t_(exhale)/t_(inhale) reaches a third threshold that is at least 1.5.

FIG. 24 illustrates a situation in which an alert is issued to a user when it is detected that the ratio t_(exhale)/t_(inhale) is too low. Another scenario in which such an alert may be issued to a user is illustrated in FIG. 32, which shows a virtual robot that the user sees via augmented reality (AR). The robot urges the user to increase the ratio between the duration of the user's exhales and inhales in order to alleviate the stress that builds up. Monitoring of respiratory parameters, and in particular, the ratio t_(exhale)/t_(inhale) can help a user address a variety of respiratory-related symptoms, as described in the following examples.

Asthma attacks are related to a person's breathing. Identifying certain changes in respiratory parameters, such as breathing rate above a predetermined threshold, can help a computer to detect an asthma attack based on the thermal measurements. Optionally, the computer utilizes a model, which was trained on previous measurements of the user taken while the user had an asthma attack, to detect the asthma attack based on the thermal measurements. FIG. 33 illustrates an asthmatic patient who receives an alert (e.g., via an augmented reality display) that his breathing rate increased to an extent that often precedes an asthma attack. In addition to the breathing rate, the computer may base its determination that an asthma attack is imminent on additional factors, such as sounds and/or movement analysis as described below.

In a first embodiment, the computer may receive recordings of the user obtained with a microphone. Such recordings may include sounds that can indicate that an asthma attack is imminent; these sounds may include: asthmatic breathing sounds, asthma wheezing, and/or coughing. Optionally, the computer analyzes the recordings to identify occurrences of one or more of the above sounds. Optionally, taking into account the recordings of the user can affect how the computer issues alerts regarding an imminent asthma attack. For example, a first alert provided to the user in response to identifying the increase in the user's breathing rate above the predetermined threshold without identifying at least one of the body sounds may be less intense than a second alert provided to the user in response to identifying both the increase in the user's breathing rate above the predetermined threshold and at least one of the body sounds. Optionally, in the example above, the first alert may not be issued to the user at all.

In a second embodiment, the computer may receive measurements obtained from a movement sensor worn by the user and configured to measure user movements. Some movements that may be measured and may be related to an asthma attack include: spasms, shivering, and/or sagittal plane movements indicative of one or more of asthma wheezing, coughing, and/or chest tightness. Optionally, the computer analyzes the measurements of the movement sensor to identify occurrences of one or more of the above movements. Optionally, considering the measured movements can affect how the computer issues alerts regarding an imminent asthma attack. For example, a first alert provided to the user in response to identifying an increase in the user's breathing rate above a predetermined threshold, without measuring a movement related to an asthma attack, is less intense than a second alert provided to the user in response to identifying the increase in the user's breathing rate above the predetermined threshold while measuring a movement related to an asthma attack.

In some embodiments, a first alert may be considered less intense than a second alert if it is less likely to draw the user's attention. For example, the first alert may not involve a sound effect or involve a low-volume effect, while the second alert may involve a sound effect (which may be louder than the first's). In another example, the first alert may involve a weaker visual cue than the second alert (or no visual cue at all). Examples of visual cues include flashing lights on a device or images brought to the foreground on a display. In still another example, the first alert is not provided to the user and therefore does not draw the user's attention (while the second alert is provided to the user).

In one embodiment, responsive to a determination that an asthma attack is imminent, the UI suggests the user to take a precaution, such as increasing t_(exhale)/t_(inhale), preforming various breathing exercises (e.g., exercises that involve holding the breath), and/or taking medication (e.g., medication administered using an inhaler), in order to decrease or prevent the severity of the imminent asthma attack. Optionally, detecting the signs of an imminent asthma attack includes identifying an increase in the breathing rate above a predetermined threshold.

Stress is also related to a person's breathing. In one embodiment, a computer receives a first indication that the user's stress level reaches a threshold and receives a second indication (i) that the ratio between exhaling and inhaling durations is below 1.5 (t_(exhale)/t_(inhale)<1.5), and/or (ii) that the user's breathing rate reached a predetermined threshold. Then the computer may command a UI to suggest the user to increase t_(exhale)/t_(inhale) to at least 1.5. Optionally, the computer receives the first indication from a wearable device, calculates t_(exhale)/t_(inhale) based on TH_(ROI) (which is indicative of the exhale stream), and commands the UI to provide the user with an auditory and/or visual feedback indicative of the change in t_(exhale)/t_(inhale) in response to the suggestion to increase the ratio. Optionally, the computer may command the UI to update the user about changes in the stress level in response to increasing t_(exhale)/t_(inhale), and may provide positive reinforcement to help the user to maintain the required ratio at least until a certain improvement in the stress level is achieved.

FIG. 25 illustrates one embodiment of a system configured to collect thermal measurements related to respiration, in which four inward-facing head-mounted thermal cameras (CAMs) are coupled to the bottom of an eyeglasses frame 181. CAMs 182 and 185 are used to take thermal measurements of regions on the right and left sides of the upper lip (186 and 187, respectively), and CAMs 183 and 184 are used to take thermal measurements of a region on the user's mouth 188 and/or a volume protruding out of the user's mouth. At least some of the ROIs may overlap, which is illustrated as vertical lines in the overlapping areas. Optionally, one or more of the CAMs includes a microbolometer focal-plane array (FPA) sensor or a thermopile FPA sensor.

In one embodiment, a computer detects whether the user is breathing mainly through the mouth or through the nose based on measurements taken by CAMs 182, 183, 184 and 185. Optionally, the system helps the user to prefer breathing through the nose instead of breathing through the mouth by notifying the user when he/she is breathing through the mouth, and/or by notifying the user that the ratio between mouth breathing and nose breathing reaches a predetermined threshold. In one embodiment, the computer detects whether the user is breathing mainly through the right nostril or through the left nostril based on measurements taken by CAMs 182 and 185.

The system may further include an inward-facing head-mounted visible-light camera 189 to take images (IM) of a region on the nose and/or mouth, which are used to calculate a respiratory parameter (e.g., detect whether the user is breathing mainly through the mouth or through the nose, detect the inhale duration, and/or detect the post-inhale pause duration). In one embodiment, one or more feature values may be generated based on IM. The feature values may be generated using various image processing techniques and represent various low-level image properties. Some examples of such features may include features generated using Gabor filters, local binary patterns and their derivatives, features generated using algorithms such as SIFT, SURF, and/or ORB, and features generated using PCA or LDA. The one or more feature values may be utilized in the calculation of the respiratory parameter in addition to feature values generated based on the thermal measurements.

In one embodiment, the inward-facing head-mounted visible-light camera 189 takes images of a region on the user's mouth, and IM are indicative of whether the mouth is open or closed. A computer utilizes a model to detect, based on IM and TH_(ROI) (such as the thermal measurements taken by at least one of CAMs 182-185), whether the user is breathing mainly through the mouth or through the nose. Optionally, the model was trained based on: a first set of TH_(ROI) taken while IM was indicative that the mouth is open, and a second set of TH_(ROI) taken while IM was indicative that the mouth is closed. Optionally, the system may help the user to prefer breathing through the nose instead of breathing through the mouth by notifying the user when he/she is breathing through the mouth, and/or by notifying the user that the ratio between mouth breathing and nose breathing reaches a predetermined threshold. FIG. 30 illustrates notifying the user that she breathes mainly through the mouth and should switch to breathing through the nose, while having a physical exercise such as spinning. FIG. 31 illustrates an exemplary UI that shows statistics about the dominant nostril and mouth breathing during the day.

In one embodiment, the inward-facing head-mounted visible-light camera 189 takes images of a region on the nose, and the computer identifies an inhale (and/or differentiates between an inhale and a breathing pause that follows the inhale) based on image processing of IM to detect movements of the nose, especially at the edges of the nostrils, which are indicative of inhaling.

FIG. 23 illustrates another embodiment of a system configured to collect thermal measurements related to respiration, in which four CAMs are coupled to a football helmet. CAMs 190 and 191 are used to take thermal measurements of regions on the right and left sides of the upper lip (appear as shaded regions on the users face), and CAMs 192 and 193 are used to take thermal measurements of a region on the user's mouth and/or a volume protruding out of the user's mouth. The illustrated CAMs are located outside of the exhale streams of the mouth and nostrils in order to maintain good measurement accuracy also when using thermal sensors such as thermopiles.

In some embodiments, the system further includes at least one in-the-ear earbud comprising a microphone to measure sounds inside the ear canal. A computer may identify an inhale based on analysis of the recordings from the earbud. Optionally, the inhale sounds measured by the earbud are stronger when the dominant nostril is the nostril closer to the ear in which the earbud is plugged in, compared to the inhale sounds measured by the earbud when the other nostril is the dominant nostril. Optionally, the computer detects whether the user is breathing mainly through the mouth or through the nose based on the thermal measurements and the sounds measured by the earbud. And then the system can help the user to prefer nasal breathing over mouth breathing by alerting the user when he/she breathes mainly through the mouth.

In some embodiments, the dominant nostril at a given time is the nostril through which most of the air is exhaled (with a closed mouth). Optionally, the dominant nostril is the nostril through which at least 70% of the air is exhaled. The different types of nostril dominance are illustrated in FIG. 34a to FIG. 34c . FIG. 34a is a schematic illustration of a left dominant nostril (note the significantly larger exhale stream from the left nostril). FIG. 34b is a schematic illustration of a right dominant nostril. And FIG. 34c is a schematic illustration of a balanced nasal breathing.

FIG. 35 is a schematic illustration of one embodiment of a system configured to identify the dominant nostril. The system includes at least one CAM 750, a computer 752, and an optional UI 754. CAM 750 may be similar to the CAMs in FIG. 25. CAM 750 takes thermal measurements of first and second ROIs below the right and left nostrils (TH_(ROI1) and TH_(ROI2), respectively) of the user. Optionally, each CAM does not occlude any of the user's mouth and nostrils. Optionally, each CAM is located less than 15 cm from the user's face and above the user's upper lip. Optionally, each CAM weighs below 10 g or below 2 g, and utilizes microbolometer or thermopile sensors. Optionally, each CAM includes multiple sensing elements that are configured to take TH_(ROI1) and/or TH_(ROI2). In one example, each CAM includes at least 6 sensing elements, and each of TH_(ROI1) and TH_(ROI2) is based on measurements of at least 3 sensing elements. Optionally, the system includes a frame to which CAM is physically coupled.

In one embodiment, the at least one CAM includes at least first and second thermal cameras (CAM1 and CAM2, respectively) that take TH_(ROI1) and TH_(ROI2), respectively, located less than 15 cm from the user's face. CAM1 is physically coupled to the right half of the frame and captures the exhale stream from the right nostril better than it captures the exhale stream from the left nostril, and CAM2 is physically coupled to the left half of the frame and captures the exhale stream from the left nostril better than it captures the exhale stream from the right nostril.

The at least one CAM may be used to capture thermal measurements of various ROIs. In one embodiment, the first region of interest (ROI₁) includes a region on the right side of the user's upper lip, and the second region of interest (ROI₂) includes a region on the left side of the user's upper lip. In another embodiment, ROI₁ includes a portion of the volume of the air below the right nostril where the exhale stream from the right nostril flows and ROI₂ includes a portion of the volume of the air below the left nostril where the exhale stream from the left nostril flows. In yet another embodiment, the at least one CAM may take thermal measurements of a region on the mouth and/or a volume protruding out of the mouth (TH_(ROI3)) of the user, which is indicative of the exhale stream from the mouth, and the computer identifies the dominant nostril also based on TH_(ROI3). Optionally, the computer may utilize TH_(ROI3) similarly to how it utilizes TH_(ROI1) and TH_(ROI2) to identify the dominant nostril (e.g., the computer may generate feature values based on TH_(ROI3), as discussed below).

The computer identifies the dominant nostril based on TH_(ROI1) and TH_(ROI2) (and possibly other data such as TH_(ROI3)), which were taken during a certain duration. Optionally, the certain duration is longer than at least one of the following durations: a duration of one exhale, a duration of one or more breathing cycles, a half a minute, a minute, and five minutes.

In one embodiment, the computer utilizes a model to identify the dominant nostril. Optionally, the model was trained based on previous TH_(ROI1), TH_(ROI2), and indications indicative of which of the nostrils was dominant while the previous TH_(ROI1) and TH_(ROI2) were taken. In one example, the computer generates feature values based on TH_(ROI1) and TH_(ROI2) (and optionally TH_(ROI3)), and utilizes the model to calculate, based on the feature values, a value indicative of which of the nostrils is dominant.

In one embodiment, the computer identifies whether the user's breathing may be considered balanced breathing. Optionally, breathing is considered balanced breathing when the streams through the right and the left nostrils are essentially equal, such as when the extent of air exhaled through the left nostril is 40% to 60% of the total of the air exhaled through the nose. Balanced breathing of a normal healthy human usually lasts 1-4 minutes during the time of switching between the dominant nostrils. Optionally, the computer notifies the user when the user's breathing is balanced. Optionally, the computer suggests to the user, via a UI, to meditate during the balanced breathing

The total time the different nostrils remain dominant may be indicative of various medical conditions. In one embodiment, when there is a significant imbalance of the daily total time of left nostril dominance compared to total time of right nostril dominance, and especially if this condition continues for two or more days (and is significantly different from the user's average statistics), it may be an indication of an approaching health problem. For example, when the total time of left nostril dominance is greater than the total time of right nostril dominance, the approaching problem may be more mentally related than physically related; and when the total time of right nostril dominance is greater than the total time of left nostril dominance, the approaching problem may be more physically related than mentally related. In another embodiment, a greater extent of left nostril dominance is related to digestion problems, inner gas, diarrhea, and male impotence; and a greater extent of right nostril dominance may be related to high blood pressure, acid reflux, and ulcers.

In one embodiment, the computer monitors nostril dominance over a certain period, and issues an alert when at least one of the following occurs: (i) a ratio between the total times of the right and left nostril dominance during the certain period reaches a threshold (e.g., the threshold may be below 0.3 or above 0.7) (ii) an average time to switch from right to left nostril dominance reaches a threshold (e.g., a threshold longer than 3 hours), and (iii) an average time to switch from left to right nostril dominance reaches a threshold.

The following are some examples of various applications in which the computer may utilize information about the dominant nostril, which is identified based on TH_(ROI1) and TH_(ROI2), in order to assist the user in various ways.

For some people, a certain dominant nostril may be associated with a higher frequency of having certain health problems, such as an asthma attack or a headache. Making a person aware of which nostril is more associated with the health problem can help the user to alleviate the health problem by switching the dominant nostril. Two examples of ways to switch the dominant nostril include: (i) to plug the current dominant nostril and breathe through the other nostril; and (ii) to lay on the side of the current dominant nostril (i.e., lying on the left side to switch from left to right dominant nostril, and vice versa). In one embodiment, the computer detects that the user is having an asthma attack, notifies the user about the current dominant nostril (which is associated with a higher frequency of asthma attacks), and suggests to switch the dominant nostril (to alleviate the asthma attack). In another embodiment, the computer detects the user has a headache, notifies the user about the current dominant nostril (which is associated with a higher frequency of headaches), and suggests to switch the dominant nostril.

Achieving balanced breathing may be a desired goal at some times. Biofeedback training may help extend the duration and/or increase the frequency at which one has balanced breathing. In one embodiment, the computer provides, via the UI, biofeedback for the user to achieve balanced breathing by playing a feedback. The feedback may be generated according to any suitable known method, such as normally playing the feedback when the breathing becomes more balanced, and stopping, rewinding, and/or dithering the feedback when the breathing becomes less balanced. Examples of feedbacks that may be used include playing a movie, running a video game, and/or playing sounds.

In a similar manner, biofeedback training may help the user to achieve a required breathing pattern, such as making a certain nostril dominant, or learning how to change the nostril from which most of the air is exhaled using thought and optionally without touching the nostrils. In one embodiment, the computer provides, via the UI, biofeedback for the user to achieve the required breathing pattern by playing a feedback. The feedback may be generated according to any suitable known method, such as playing a first sound when the use exhales more air from the right nostril than the left nostril, playing a second sound when the use exhales more air from the left nostril than the right nostril, and playing a third sound when the use exhales essentially the same from the right and left nostrils.

In one embodiment, the length of the exhale stream is considered as the distance from the nose at which the exhale stream can still be detected. For each person, there is a threshold that may change during the day and responsive to different situations. When the length of the exhale stream is below the threshold, it may indicate that the person is calm; and when the length of the exhale stream is longer than the threshold, it may indicate excitement. In general, the shorter the length of the exhale stream the less energy is invested in the breathing process and the less stress the person experiences. An exception may be arduous physical activity (which can increase the length of the exhale stream due to larger volumes of air that are breathed). In one embodiment, TH_(ROI1) and TH_(ROI2) are indicative of the length of the exhale stream, and the computer calculates level of excitement of the user based on the length of the exhale stream. Optionally, the longer the length, the higher the excitement/stress, and vice versa. Additionally, the relationship between the length of the exhale stream and the level of excitement may be a function of parameters such as the time in day, the dominant nostril, the user's mental state, the user's physiological state, the environmental air quality, and/or the temperature of the environment. In one example, the at least one CAM uses multiple sensing elements to take thermal measurements of regions located at different lengths below the nostrils. In this example, the larger the number of the sensing elements that detect the exhale stream, the longer the length of the exhale stream. Optionally, the amplitude of the temperature changes measured by the sensing elements is also used to estimate the length, shape, and/or uniformity of the exhale stream.

Ancient yoga texts teach that learning to extend the duration of the time gaps between inhaling and exhaling, and/or between exhaling and inhaling, increases life span. In one embodiment, the computer assists the user to extend the duration of the time gap between inhaling and exhaling by performing at least one of the following: (i) calculating the average time gap between inhaling and exhaling over a predetermined duration, and providing the calculation to the user via a user interface (UI), (ii) calculating the average time gap between inhaling and exhaling over a first predetermined duration, and reminding the user via the UI to practice extending the duration when the average time gap is shorter than a first predetermined threshold, and (iii) calculating the average time gap between inhaling and exhaling over a second predetermined duration, and encouraging the user via the UI when the average time gap reaches a second predetermined threshold. It is to be noted that to stop breathing after exhaling is considered more beneficial but also more dangerous, therefore the system may enable the user to select different required durations for stopping the breathing after inhaling and for stopping breathing after exhaling.

Typically, the dominant nostril switches sides throughout the day, with the duration between each switch varying, depending on the individual and other factors. Disruption of the typical nasal switching cycle may be indicative of physiological imbalance, emotional imbalance, and/or sickness. For example, slower switching of the dominant nostril may be, in some cases, a precursor of some diseases. In one embodiment, the computer learns the typical sequence of switching between dominant nostrils based on previous measurements of the user taken over more than a week, and issues an alert upon detecting an irregularity in the sequence of changes between the dominant nostrils. In one example, the irregularity involves a switching of the dominant nostril within a period of time that is shorter than a certain period typical for the user, such as shorter than forty minutes. In another example, the irregularity involves a lack of switching of the dominant nostril for a period that is greater than a certain period typical for the user, such as longer than three hours. In yet another example, the cycles of the dominant nostril may be described as a time series (e.g., stating for each minute a value indicative of the dominant nostril). In this example, the computer may have a record of previous time series of the user, acquired when the user was healthy, and the computer may compare the time series to one or more of the previous time series in order to determine whether a sufficiently similar match is found. A lack of such a similar match may be indicative of the irregularity.

The following is a discussion of the role of nostril dominance and other breathing aspects in Asian philosophy. According to Asian philosophy, and specifically the Vedas, all objects are made of the Five Great Elements, also known as the Classical elements, which include earth, water, fire, air, and space. The great elements represent types of energy, but they are related to the physical elements they are called after. During left or right nostril dominance, just one element is typically dominant in the body, and this is reflected in the form of the exhale stream (during balanced breath two elements may share dominance). When dominance in breathing is not forced, each of the five great elements in turn may become dominant and then cedes dominance to the next one. The normal order of dominance according to one text is: air, fire, earth, water, and space. The relative ratios of duration of dominance are: earth—5, water—4, fire—3, air—2, space—1. The dominant element affects breathing in two ways: the length of the exhale and the shape of the exhale stream (SHAPE). The average lengths and shapes of the outbreath are as follows according to one yoga textbook: earth—about 24 cm, straight out of the center of the nostril. Water—about 32 cm length, coming from the bottom of the nostril in a slight downward direction. Fire—8 cm, coming from the top of the nostril with an upward slant. Air—about 16 cm, coming from the external side of the nostril (left for the left nostril and right for the right nostril) with a slant outside. Space—very light and short breath from all parts of the nostril.

In one embodiment, the computer identifies, based on TH_(ROI1) and TH_(ROI2), the dominant element out of the five elements. Optionally, the computer monitors if relative durations and order of elements' dominance is regular, i.e. according to the order and duration ratios specified and optionally with approximate length as prescribed, or there is some irregularity. In one embodiment, irregularity may indicate a potential problem with the associated gland: for earth—ovaries or testes/prostate, water—adrenal, fire—intestines, air—none, space—thyroid and para-thyroid. In another embodiment, irregularity may indicate a potential mental and/or physiological problem(s).

If an element's dominance time (as evident from breathing characteristics) is too long, it may be balanced (reduced) by consuming appropriate food and/or drink. For example, air dominance can be reduced by consuming heavy oily food, fire dominance can be reduced by drinking water or by consuming water-absorbing food like buckwheat, and earth dominance can be reduced by eating light food with a lot of fiber.

If a dominant element is too weak (i.e., judging by breathing characteristics compared to the yardstick for that element, or comparing the SHAPE to a baseline SHAPE), it can be strengthened. For example, air dominance can be strengthened by active physical movement, fire dominance can be strengthened by breath-of-fire (from kundalini yoga), water dominance can be strengthened by drinking, earth can be strengthened by eating proteins and oily food, and space dominance can be strengthened by visualizing a picture that grows and shrinks in size.

As discussed above, the shape of the exhale stream (SHAPE) from the nostrils changes over time. With the at least one CAM it is possible, in some embodiments, to obtain measurements indicative of at least some of the different typical SHAPEs. A non-limiting reason for the system's ability to measure the different SHAPEs is that the exhale stream has a higher temperature than both the typical temperature of the environment and the typical temperature of the upper lip. As a result, the particles of the exhale stream emit at a higher power than both the environment and the upper lip, which enables CAM to measure the SHAPE over time.

As discussed above, different SHAPEs may be characterized by different 3D shape parameters (e.g., the angle from which the exhale stream blows from a nostril, the width of the exhale stream, the length of the exhale stream, and other parameters that are indicative of the 3D SHAPE). Additionally, different SHAPEs may be associated with different states of the user, such as different physiological and/or mental conditions the user may be in. In some embodiments, the computer calculates the SHAPE based on TH_(ROI1) and TH_(ROI2). Optionally, calculating the shape involves calculating values of one or more parameters that characterize the exhale stream's shape (e.g., parameters related to the 3D SHAPE). Optionally, calculating the SHAPE involves generating a reference pattern for the SHAPE. For example, the reference pattern may be a consensus image and/or heat map that is based on TH_(ROI1) and TH_(ROI2) taken over multiple breaths.

In other embodiments, the computer identifies a SHAPE based on TH_(ROI1) and TH_(ROI2). Optionally, the identified SHAPE belongs to a set that includes at least first and second SHAPEs, between which the computer differentiates. Optionally, the first and second SHAPEs are indicative of at least one of the following: two of the five great elements according to the Vedas, two different emotional states of the user, two different moods of the user, two different energetic levels of the user, and a healthy state of the user versus an unhealthy state of the user. In one example, the first SHAPE is indicative of a powerful alert energetic level, while the second SHAPE is indicative of a tired energetic level, and the computer uses this information to improve computerized interactions with the user.

The SHAPE may be related to the dominant nostril at the time. In one embodiment, the first SHAPE occurs more frequently when the right nostril is dominant, and the second SHAPE occurs more frequently when the left nostril is dominant. In another embodiment, both the first and the second SHAPEs occur more frequently when the right nostril is dominant.

In one example, differentiating between the first and second SHAPEs means that there are certain first TH_(ROI1) and TH_(ROI2) that the computer identifies as corresponding to the first SAHPE and not as corresponding to the second SHAPE, and there are certain second TH_(ROI1) and TH_(ROI2) that the computer identifies as corresponding to the second SHAPR and as not corresponding to the first SHAPE. In another example, differentiating between first and second SHAPEs means that there are certain third TH_(ROI1) and TH_(ROI2) that the computer identifies as having a higher affinity to the first SHAPE compared to their affinity to the second SHAPE, and there are certain fourth TH_(ROI1) and TH_(ROI2) that the computer identifies as having a higher affinity to the second SHAPE compared to their affinity to the first SHAPE.

In some embodiments, the SHAPE is identified by the computer based on TH_(ROI1), TH_(ROI2), and optionally other sources of data. Since the SHAPE does not typically change between consecutive breaths, detecting the shape of the exhale may be done based on multiple measurements of multiple exhales. Using such multiple measurements can increase the accuracy of the identification of the shape. In one example, the first and second SHAPEs are identified based on first and second sets of TH_(ROI1) and TH_(ROI2) taken during multiple exhales over first and second non-overlapping respective durations, each longer than a minute.

The computer may utilize different approaches to identify the SHAPE. In one embodiment, the computer may compare TH_(ROI1) and TH_(ROI2) to one or more reference patterns to determine whether TH_(ROI1) and TH_(ROI2) are similar to a reference pattern from among the one or more reference patterns. For example, if the similarity to a reference pattern reaches a threshold, the exhale stream measured with TH_(ROI1) and TH_(ROI2) may be identified as having the shape corresponding to the shape of the reference pattern. Determining whether TH_(ROI1) and TH_(ROI2) are similar to a reference pattern may be done using various image similarity functions, such as determining the distance between each pixel in the reference pattern and its counterpart in TH_(ROI1) and TH_(ROI2). One way this can be done is by converting TH_(ROI1) and TH_(ROI2) into a vector of pixel temperatures, and comparing it to a vector of the reference pattern (using some form of vector similarity metric like a dot product or the L2 norm).

The one or more reference patterns may be generated in different ways. In one embodiment, the one or more reference patterns are generated based on previous TH_(ROI1) and TH_(ROI2) of the user taken on different days. Optionally, the SHAPEs were known while previous TH_(ROI1) and TH_(ROI2) of the user taken. In one example, the SHAPE is associated with a state of the user at the time (e.g., relaxed vs. anxious). In another example, the SHAPE may be determined using an external thermal camera (which is not head-mounted). In yet another example, the SHAPE is determined by manual annotation. In one embodiment, the one or more reference patterns are generated based on previous TH_(ROI1) and TH_(ROI2) of one or more other users.

In some embodiments, the SHAPE may be discovered through clustering. Optionally, the computer may cluster sets of previous TH_(ROI1) and TH_(ROI2) of the user into clusters. Where sets of TH_(ROI1) and TH_(ROI2) in the same cluster are similar to each other and the exhale streams they measured are assumed to have the same shape. Thus, each of the clusters may be associated with a certain SHAPE to which it corresponds. In one example, the clusters include at least first and second clusters that correspond to the aforementioned first and second SHAPEs.

The computer may utilize a machine learning-based model to identify the SHAPE. In one embodiment, the computer generates feature values based on TH_(ROI1) and TH_(ROI2), and utilizes a model to classify TH_(ROI1) and TH_(ROI2) to a class corresponding to the SHAPE. Optionally, the class corresponds to the aforementioned first or second shapes. Optionally, the model is trained based on previous TH_(ROI1) and TH_(ROI2) of the user taken during different days.

In one embodiment, the computer receives an indication of the user's breathing rate, and uses this information along with the SHAPE at that time in order to suggest to the user to perform various activities and/or alert the user. Optionally, the indication of the user's breathing rate is calculated based on TH_(ROI1) and TH_(ROI2). In one example, the SHAPE is correlative with the state of the user, and different states combined with different breathing rates may have different meaning, which cause the computer to suggest different activities. The different activities may vary from different work/learning related activities to different physical activities to different treatments. In one example, the computer suggests to the user, via the UI, to perform a first activity in response to detecting that the breathing rate reached a threshold while identifying the first SHAPE. However, the computer suggest to the user to perform a second activity, which is different from the first activity, in response to detecting that the breathing rate reached the threshold while identifying the second SHAPE. In another example, the computer alerts the user, via the UI, in response to detecting that the breathing rate reached a threshold while identifying the first SHAPE, and the computer does not alert the user in response to detecting that the breathing rate reached the threshold while identifying the second SHAPE. In this example, the SHAPE may be correlated with the state of the user, and different states may be associated with different normal breathing rates. When the difference between the current breathing rate and the normal breathing rate (associated with the current SHAPE) reaches a threshold, the user may be in an abnormal state that warrants an alert.

In another embodiment, the computer configures a software agent that prioritizes activities for the user based on the identified SHAPE, such that a first activity is prioritized over a second activity responsive to identifying the first SHAPE, and the second activity is prioritized over the first activity responsive to identifying the second SHAPE. It is noted that the system may prioritize different activities for different SHAPEs also when the measured breathing rate and respiration volume are the same.

In still another embodiment, the computer learns a flow of typical changes between different SHAPEs based on previous measurements of the user, and issues an alert upon detecting an irregularity related to a flow of changes between the SHAPEs. For example, the irregularity may involve a new SHAPE, more frequent changes between SHAPEs, having certain SHAPEs for more or less time than usual, etc.

In yet another embodiment, the computer receives data about types of foods consumed by the user, stores the data in a memory, and finds correlations between the SHAPEs and the types of foods. These correlations may be used to make suggestions to the user. For example, the computer may suggest the user to eat a first type of food responsive to identifying the first SHAPE, and suggest the user to eat a second type of food responsive to identifying the second SHAPE. According to Ayurveda medicine, it is preferred to eat according to the three do

has and the five great elements. In times when the SHAPE is indicative of the dominant element (out of the five great elements), the computer may guide the user which types of food suit the identified dominant element, and/or may help the user to avoid inappropriate types of foods by identifying the types of food the user eats (and/or is about to eat), and alert the user when the identified food is inappropriate to the current dominant element (that was identified based on the SHAPE).

Data obtained from monitoring the dominant nostril can be utilized to make suggestions of activities for the user. FIG. 36a illustrates one embodiment of a system configured to suggest activities according to the dominant nostril. The system includes a sensor 451 for taking measurements 454 indicative of which of the user's nostrils is dominant at the time the measurements 454 were taken. Optionally, the sensor 451 is one or more thermal cameras, such as the thermal cameras illustrated in FIG. 25, however, as discussed below, other types of sensors may be utilized to take the measurements 454. The system also includes a computer 455 and optionally includes a UI 456.

The computer 455 predicts, based on the measurements 454, which of the user's nostrils will be the dominant nostril at a future time. Optionally, responsive to predicting that the right nostril will be dominant at the future time, the computer 455 suggests having at the future time a first activity, which is more suitable for a right dominant nostril than a second activity. Optionally, responsive to predicting that the left nostril will be dominant at the future time, the computer suggests having at the future time the second activity, which is more suitable for a left dominant nostril than the first activity. Optionally, the computer 455 suggests activities utilizing the UI 456. In one example, the first activity requires more verbal-analytical skills and less spatial skills compared to the second activity. In another example, the first activity requires more logic and/or locomotive skills compared to the second activity, and less empathy and/or imagination. In another example, the second activity requires more creativity and less physical effort compared to the first activity.

The suggestions of activities described above may be based on the premise that the dominant nostril is indicative of which of the user's brain hemispheres is more effective at performing activities that are associated with it. It is typically assumed that the left side of the user's brain is expected to be more effective at performing tasks when the right nostril is dominant (compared to when the left nostril is dominant). Conversely, the right side of the user's brain is expected to be more effective at performing tasks when the left nostril is dominant (compared to when the right nostril is dominant). The right hemisphere is usually believed to be better at expressive and creative tasks. Some of the abilities associated with the right hemisphere include recognizing faces, expressing emotions, music, reading emotions, color, images, intuition, and creativity. The left hemisphere is usually believed to be adept to tasks that involve logic, language, and analytical thinking. The left hemisphere is usually described as being better at language, logic, critical thinking, numbers, and reasoning. Thus, certain activities, which require certain skills that are associated with a certain hemisphere, may be more suitable to perform when one nostril is dominant compared to when the other nostril is dominant.

Additionally or alternatively, the suggestions of activities described above may be based on empirical data of the performances of the user and/or performances of other users. By analyzing the user's performances versus the dominant nostril (and optionally other parameters), and/or using big data analysis of the measured performances of many users versus their dominant nostril (and optionally other parameters), it is possible to identify a first set of activities that are statistically significantly more successfully achieved during right dominant nostril, a second set of activities that are statistically significantly more successfully achieved during left dominant nostril, and a third set of activities that are statistically significantly more successfully achieved during a balanced nasal breathing.

To predict the dominant nostril at the future time, the computer 455 relies on the measurements 454, which were taken prior to a current time, at which the prediction is made. Optionally, the future time may be at least five minutes after the current time, at least thirty minutes after the current time, at least one hour after the current time, at least three hours after the current time, or at least six hours after the current time.

In one embodiment, the computer 455 utilizes the measurements 454 to determine when the dominant nostril last switched (before the current time), and uses this information to predict when it will switch next (possibly multiple times). Thus, the computer can extrapolate, based on the measurements 454, a timeline until the future time, indicating which nostril is dominant at different times until (and including) the future time. Optionally, information useful for determining the time line (such as the time each nostril remains dominant) may be based on the measurements 454 and/or previous measurements of the user taken with the sensor 451 during different days.

In another embodiment, the computer 455 predicts the dominant nostril at the future by generating feature values and utilizing a machine learning-based model to estimate the dominant nostril at the future time (e.g., left nostril dominance, right nostril dominance, or balanced breathing). Optionally, the feature values comprise one or more feature values describing aspects of the future time such as the time to which it corresponds (e.g., how much time ahead the future time is), the location the user is expected to be at the future time, and/or an activity the user is expected to partake at the future time. Optionally, the feature values may include one or more features values corresponding to a state of the user at an earlier time that precedes the future time, such as the user's dominant nostril (e.g., as determine based on the measurements 454), manipulation of the dominant nostril performed by the user recently, previous measurements of the user taken after the user manipulated the dominant nostril and/or practiced pranayama and/or listened to brainwave entrainment, an activity the user had during the earlier time, and/or values of physiological signals of the user at the earlier time. In one embodiment, the machine learning-based model is trained based on samples that include measurements 454 taken at certain earlier times and their corresponding dominant nostrils following certain durations after the certain earlier times.

When a first activity is suggested for the future time (over the second activity), it typically means that the first activity is to be preferred over the second activity. Optionally, to suggest having the first activity at the future time means that the computer schedules the first activity at the future time and does not schedule the second activity at the future time. Additionally or alternatively, to suggest having the first activity at the future time means that the computer 455 ranks the first activity at the future time higher than it ranks the second activity at the future time. Optionally, when the first activity is ranked higher than the second activity it means that the first activity is given a stronger recommendation than the second activity. For example, a stronger recommendation may involve the first activity being suggested by displaying it first on a list of suggested activities. In another example, a stronger recommendation may involve suggesting the first activity with a larger image, a more prominent visual effect, and/or a more noticeable auditory signal than the one used to suggest the second activity.

The computer 455 may utilize a determination of which nostril is dominant at the current time and/or a prediction of which nostril will be dominant at the future in order to assist the user in performing activities at suitable times. In a first embodiment, the computer 455 assists the user to spend more time eating certain types of food when the right nostril is dominant. Additionally or alternatively, the computer 455 further assists the user to spend less time eating the certain types of food when the left nostril is dominant. In one example, the computer 455 may assist the user by identifying that the user starts looking for food during left nostril dominance, and reminding the user that eating while the left nostril is dominant is probably due to emotional reasons. In another example, the computer 455 may arrange the user's schedule such that at least 60% of the occurrences of lunch and/or dinner are planned to a time when the right nostril is dominant. Optionally, the computer 455 recommends to the user to have the main meal of the day while the right nostril is dominant. In a second embodiment, the computer 455 assists the user to increase the time spent at the toilet defecating while the right nostril is dominant. Optionally, the computer 455 recommends to the user to spend less time at the toilet defecating while the left nostril is dominant. For example, the computer 455 may recommend to go on a bathroom break when the right nostril is dominant. Optionally, the computer 455 may assist the user to decrease defecating during times of left nostril dominance by reminding the user that it is preferred to defecate during right nostril dominance, especially when suffering from constipation. In a third embodiment, the activity involves creativity, such as creating art, and the computer 455 assists the user to spend more time on the creative activity when the left nostril is dominant.

It is recommended to perform some activities when the breathing through the nose is balanced. In one embodiment, the computer 455 identifies, based on the measurements 454, times in which the breathing through the nose is balanced, and suggests a third activity for those times. Optionally, the third activity is more suitable for balanced breathing compared to the first and second activities. Optionally, the third activity requires higher self-awareness compared to the first and second activities. For example, the third activity may include a spiritual practice (such as meditating or praying), while the first and second activities do not include spiritual practices.

Various hardware configurations may be utilized in different embodiments of the system configured to suggest activities according to the dominant nostril, in order to take the measurements 454 of the user.

In a first embodiment, the system includes a CAM that takes thermal measurements of a region below the user's nostrils (e.g., CAM 183 or CAM 184). In this embodiment, identifying the dominant nostril and/or whether the breathing is balanced may be done by the computer 455 based on signal processing of the thermal measurements taken by CAM.

In a second embodiment, the sensor 451 includes one or more implanted sensors located around the area of the nostrils. In this embodiment, identification of the dominant nostril and/or whether the breathing is balanced may be done based on signal processing of the measurements of the implanted sensors.

In a third embodiment, the sensor 451 includes right and left in-the-ear earbuds comprising microphones, configured to measure sounds inside the right and left ear canals; the computer 455 identifies the dominant nostril based on analysis of the recordings from the earbuds. For example, the computer 455 may identify the dominant nostril based on the assumption that the inhale sounds measured by the in-the-ear earbud in the dominant side are stronger than the inhale sounds measured by the in-the-ear earbud in the non-dominant side.

In a fourth embodiment, the system includes a frame configured to be worn on the user's head, and the sensor 451 comprises a visible-light camera; the visible-light camera is physically coupled to the frame, and takes images of a region on the user's nose. For example, the computer 455 may identify the dominant nostril based on analyzing the images of the nose by identifying movements of the nose, especially at the edges of the nostrils.

In a fifth embodiment, the sensor 451 includes thermistors that are in contact with the nostrils and/or the upper lip in order to take the measurements. Optionally, the dominant nostril may be identified based on signal processing of the thermistors' measurements.

In a sixth embodiment, the sensor 451 includes anemometers located inside the breathing streams of the nostrils in order to take the measurements. Optionally, the dominant nostril is identified based on signal processing of the anemometers' measurements.

In a seventh embodiment, the sensor 451 includes a non-wearable IR camera pointed to the area around the nostrils in order to take the measurements. Optionally, the dominant nostril is identified based on image processing of the measurements of the non-wearable IR camera.

The suggestions provided by the computer 455 may be done as part of various programs that may benefit the user. Optionally, the computer 455 provides functionality of at least one of the following programs: a virtual assistant (i.e., a software agent), a calendar management program, a priority management program, a project management program, a “to do” list program, a work schedule program, and a self-learning program.

Some embodiments of the system may involve notification of the user about which of the nostrils is dominant at a given time (e.g., via UI 456). Optionally, the notification involves providing a user with an indication (e.g., via sound and/or an image) when the dominant nostril changes and/or every certain period of time (e.g., every hour). Additionally or alternatively, notifying the user about which of the nostrils is dominant may involve utilizing different themes for UI 456. In one example, a first theme for UI 456 is utilized when the right nostril is the dominant nostril, and a second theme for UI 456 is utilized when the left nostril is the dominant nostril. Optionally, the first theme is more logical than the second theme (e.g., presenting data and/or suggestions involves providing more facts and/or detailed explanations), and the second theme is more emotional than the first theme (e.g., presenting data and/or suggestions includes more emotional phrases, abstract images, social-related data, and/or less factual information).

In one embodiment, the computer 455 is programmed to converse with the user according to at least first and second modes. The first mode is perceived by the user as more logical than the second mode, and the second mode is perceived by the user as more emotional than the first mode. The computer 455 uses, on average, the first mode more frequently than the second mode when the right nostril is the dominant nostril, and uses, on average, the second mode more frequently than the first mode when the left nostril is the dominant nostril. Examples of logical speech include sentences built around numbers and facts, while emotional speech includes sentences built around emotions and intuition.

The following is a description of steps involved in one embodiment of a method for suggesting activities according to the dominant nostril. The steps described below may be used by systems modeled according to FIG. 36a , and may be performed by running a computer program having instructions for implementing the method. Optionally, the instructions may be stored on a computer-readable medium, which may optionally be a non-transitory computer-readable medium. In response to execution by a system including a processor and memory, the instructions cause the system to perform operations of the method.

In one embodiment, the method for alerting about stress includes at least the following steps: In Step 1, taking, utilizing a sensor, measurements of a user, which are indicative of the user's dominant nostril. In Step 2, predicting, based on the measurements, which of the user's nostrils will be the dominant nostril at a future time (that occurs after the measurements in Step 1 were taken). And In Step 3, responsive to predicting that the right nostril will be dominant at the future time, suggesting having at the future time a first activity, which is more suitable for a right dominant nostril than a second activity. Optionally, responsive to predicting that the left nostril will be dominant at the future time, this step involves suggesting having at the future time the second activity, which is more suitable for a left dominant nostril than the first activity. Optionally, the method further includes assisting the user to decrease eating certain types of food during left nostril dominance, and assisting the user to schedule the main meal of the day during right nostril dominance. Optionally, the method further includes learning the typical sequence of switching between dominant nostrils based on previous measurements of the user taken over more than a week, and alerting upon detecting an irregularity in the sequence of changes between the dominant nostrils.

In some embodiments, a system is configured to detect a physiological response based on respiratory parameters. Optionally, the physiological response is stress. Optionally, the respiratory parameters include the breathing rate and breathing rate variability (which is discussed further below).

The breathing rate variability (BRV) is a value that is indicative of the physiological phenomenon of variations between consecutive breathes, observed during a certain period of time (e.g., a minute). In a similar fashion to heart rate variability (HRV), which is the physiological phenomenon of variations between consecutive heartbeats, the extent of BRV can be indicative of various physiological phenomena, such as stress and/or physiological state.

In one embodiment, stress is detected based on thermal measurements of ROIs indicative of respiration performances, such as the mouth area, the upper lip area, and/or an air volume below the nostrils where the exhale from the nose flows. Optionally, TH_(ROI) may be utilized to calculate various respiratory parameters, which include the breathing rate and/or the BRV.

The duration between successive breaths (such as the time between starting successive exhales) and/or breathing irregularity may be calculated using various methods, such as geometric methods, frequency-domain methods, and/or non-linear methods. The computer may calculate the BRV based on TH_(ROI) taken during different periods of time, such as at least one minute long or at least 5 minutes long.

In one embodiment, the breathing rate variability (BRV) and the breathing rate (BR) are utilized by a computer in order to detect when the user is stressed. Optionally, elevated BRV in addition to elevated BR may serve as an indicator of stress. Optionally, elevated BRV, even when the BR is reduced, may serve as an indicator of stress. For example, the computer may calculate BR₁ and BRV₁ based on TH_(ROI) taken during a first period, calculate BR₂ and BRV₂ based on TH_(ROI) taken during a second following period, and determine that the user's stress level is higher at the second period relative to the first period because (BRV₁<BRV₂), even though (BR₁>BR₂).

In one embodiment, the computer calculates the stress level based on comparing BR and BRV to various thresholds that correspond to different stress levels. In one example, having a high BRV may lower the threshold on BR that is required in order to detect stress.

In another embodiment, the computer may utilize a machine learning-based model in order to detect the stress level. Optionally, the computer utilizes TH_(ROI) to generate feature values indicative of the BR and/or the BRV, and the model was trained based on samples that each include feature values based on TH_(ROI) and labels indicative of the user's stress level.

Some embodiments described herein involve utilization of at least one inward-facing head-mounted thermal cameras (such a camera is denoted below CAM) to take thermal measurements of a region below the nostrils (these measurements are denoted below TH_(RBN)). TH_(RBN) are indicative of an exhale stream of the user, such as air exhaled from a nostril and/or the mouth of the user. Since exhaled air usually has a different temperature than the environment and/or the human skin, TH_(RBN) can provide indications regarding the user's respiratory activity, such as the breathing rate, whether exhaling is done through the mouth or nose, the respiration volume, and other respiratory parameters described herein. Additionally or alternatively, TH_(RBN) may be used to calculate an aerobic activity parameter (as illustrated in FIG. 37a ) and/or a coaching indication (as illustrated in FIG. 37b ). The following is a description of embodiments of such systems that utilize TH_(RBN) for such respiratory-related applications. The systems illustrated in FIG. 37a and FIG. 37b include at least one CAM and a computer.

The at least one CAM may include various combinations of one or more CAMs, as described in the various examples given in this disclosure of embodiments that include a single inward-facing head-mounted thermal camera that measures TH_(RBN) (e.g., a single CAM coupled to the bottom of one of the sides of a frame worn by the user) or multiple CAMs (e.g., multiple CAMs coupled to different locations on a frame worn by the user). In one example, the at least one CAM includes CAM 681 illustrated in FIG. 37a . In other examples, the at least one CAM may include one or more of the CAMs described in various figures in this disclosure. For example, FIG. 25 illustrates one embodiment of an HMS that may be used to measure TH_(RBN), in which at least one CAM (four CAMs in this case), is coupled to the bottom of an eyeglasses frame 181. CAMs 182 and 185 are used to take thermal measurements of regions on the right and left sides of the upper lip (186 and 187, respectively), and CAMs 183 and 184 are used to take thermal measurements of a region on the user's mouth 188 and/or a volume protruding out of the user's mouth. At least some of the ROIs may overlap, which is illustrated as vertical lines in the overlapping areas. Optionally, a CAM from among the one or more of the CAMs includes at least one of the following sensors: a thermopile sensor, and a microbolometer sensor. Optionally, a CAM from among the one or more of the CAMs includes a microbolometer focal-plane array (FPA) sensor or a thermopile FPA sensor. Additional examples of systems that include at least one CAM that may be used to take TH_(RBN) are illustrated in FIG. 9 to FIG. 11 as well as FIG. 3b (one or more of the cameras 22, 24, and 28).

In some embodiments, each CAM, from among the at least one CAM, is physically coupled to frame worn on the head of a user (whose measurements are being taken), such as frames of eyeglasses, an augmented reality HMS, a virtual reality HMS, or a mixed reality HMS. In one example, each CAM, from among the at least one CAM, is physically coupled to frame 680. Optionally, each CAM, from among the at least one CAM, is located less than 15 cm from the user's face and weighs less than 10 g. Optionally, the frame holds each CAM, from among the at least one CAM, such that the CAM does not protrude beyond the tip of the user's nose.

In one embodiment, each CAM, from among the at least one CAM, is located above the user's upper lip and less than 15 cm from the user's face, and does not occlude any of the user's mouth and nostrils. Optionally, TH_(RBN) include thermal measurements of at least one of first and second regions below right and left nostrils (TH_(RBN1) and TH_(RBN2), respectively) of the user, which are indicative of exhale streams from the right and left nostrils, respectively. Additionally or alternatively, TH_(RBN) may include thermal measurements of at least one of a region on the mouth and a volume protruding out of the mouth (TH_(RBN3)) of the user, indicative of exhale stream from the mouth.

The following is a description of one possible utilization of TH_(RBN), which involves calculation of an aerobic activity parameter of a user. FIG. 37a illustrates an embodiment of a system configured to estimate an aerobic activity parameter 688. The system includes at least one CAM (as described above) that is used to measure TH_(RBN) 683 and a computer 686. Some embodiments of the system may optionally include additional elements, such as the frame 680, a head-mounted inward-facing video camera 682, a sensor 684, and a user interface 689.

The computer 686 is configured, in one embodiment, to calculate, based on TH_(RBN) (taken by the at least one CAM), the aerobic activity parameter 688. Optionally, the aerobic activity parameter 688 is indicative of one or more of the following values: oxygen consumption (VO₂), maximal oxygen consumption (VO₂ max), and energy expenditure (EE). Optionally, the computer 686 may utilize additional inputs to calculate the aerobic activity parameter such as measurements of the heart rate (HR) of the user, values of the activity level of the user, and/or various statistics about the user (e.g., age, weight, height, gender, etc.).

Herein, VO₂ refers to a value indicative of the rate of oxygen consumption. This value typically rises as physical activity becomes more strenuous and the body has a larger demand for oxygen for various metabolic processes. In one example, VO₂ is a value expressed in units of mL/(kg·min), or some other units proportional to mL/(kg·min). VO₂ max refers to a value indicative of the maximal rate of oxygen consumption; typically, the higher VO₂ max, the higher the person's cardiorespiratory fitness and endurance capacity during prolonged exercises. EE may refer to a value indicative of the rate of energy expenditure, and may be expressed in various units such as kcal/h, or some other unit proportional to kcal/h. When the rate of energy expenditure is integrated over a period time, then EE may refer to a value indicative of the total energy expenditure over the period of time, and may be a value expressed in calories or some other unit proportional to calories.

Since direct measurements of aerobic activity parameters such as VO₂, VO₂ max, and EE are typically cumbersome uncomfortable procedures that need to be performed in controlled settings (e.g., running on a treadmill while wearing a mask that is used to collect and analyze exhaled breath), these values are often estimated based on various values that are correlated to some extent with the aerobic activity parameters. For example, various formulas and/or models were developed to estimate values of aerobic activity parameters from values such as heart rate (and changes from resting heart rate), activity level, and various statistics e.g., age, weight, height, gender, etc.)

Embodiments described herein utilize values indicative of the respiratory activity, such as TH_(RBN) 683 and/or values derived from TH_(RBN) 683 (e.g., respiration rate and/or respiration volume) in order to enhance the accuracy of the estimation of aerobic activity parameters. Respiration parameters such as the respiration rate and/or respiration volume are tightly related to parameters such as VO₂ and EE and thus provide additional information about these parameters. Additionally, respiration values can help reduce inaccuracies in estimation of aerobic activity parameters due to various artifacts. For example, during changes in body positions (e.g., postural hypotension), there are usually only minor changes in VO₂ and respiration but major changes in HR. In another example, a value such as the respiration rate can distinguish between non-metabolic (e.g. mental and non-exercise related physical stress) and metabolic (physical activity induced) increases in HR. Thus, for example, using respiration data in addition to other values (e.g., HR) may provide better estimations of the values of the aerobic activity parameters, compared to estimations that do not involve respiration data.

The computer 686 may utilize various approaches in order to estimate aerobic activity parameters based on data that includes TH_(RBN) 683 and/or values derived from TH_(RBN). In one embodiment, the computer 686 generates feature values based on data comprising TH_(RBN), and utilizes a model 687 to calculate the aerobic activity parameter 688 based on the feature values. Optionally, the model 687 is trained based on data indicative of aerobic activity of multiple users (e.g., data that includes physiological signals such as respiratory rate, heart rate, etc., of the multiple users). Additionally or alternatively, the model 687 is trained based on data that includes previous TH_(RBN) of the multiple users and values of the aerobic activity parameter of the multiple users corresponding to when the previous TH_(RBN) were taken. For example, the training data includes samples, each sample comprising: (i) feature values were generated from certain pervious TH_(RBN) of a certain user taken during certain period of time, and (ii) a label generated based on a measurement of the value of the aerobic activity parameter of the certain user during the certain period of time (i.e., the value of VO₂, VO₂ max, or EE, as measured during the certain period of time).

The computer 686 may generate various types of feature values that are used to estimate the value of the aerobic activity parameter 688. Optionally, the computer 686 generates one or more feature values, based on TH_(RBN) 683, which may be any of the feature values described in this disclosure that are used to detect a physiological response, and in particular, the one or more feature values may be any of the feature values described in this disclosure as being pertinent to calculation of a respiratory parameter. Additionally or alternatively, feature values generated by the computer 686 may include: time series data comprising values measured by a CAM, average values of certain pixels of a CAM, and/or values measured at certain times by the certain pixels. Additionally or alternatively, at least some of the feature values generated by the computer 686 may include measurements of the environment in which the user is in and/or indications of confounding factors (e.g., indications of use of medication).

In some embodiments, feature values generated by the computer 686 may include values of one or more respiratory parameters calculated based on TH_(RBN) 683. In one example, the feature values generated by the computer 686 include a feature value indicative of a ratio between an extent to which the user breathed via the mouth and an extent to which the user breathed via the nose. In another example, the feature values generated by the computer 686 include a feature value indicative of a ratio between durations of exhales of the user and duration of inhales of the user.

In some embodiment, the feature values generated by the computer 686 may include a feature value indicative of heart rate (HR) of the user while TH_(RBN) 683 were taken. Additionally or alternatively, the feature values generated by the computer 686 include another feature value indicative of cardiac activity such as heart rate variability (HRV). For example, measurements indicative of HR and/or HRV may be obtained by a different sensor, which is not a CAM, such as a photoplethysmogram (PPG) sensor that is head-mounted (e.g., coupled to the temple of eyeglasses worn by the user), coupled to a wearable device such as a smartwatch, or embedded in a garment worn by the user, such as a smart shirt.

In addition to data describing physiological signals mentioned above, in some embodiments, data used to generate at least some of the feature values by the computer 686 may include various values describing the user, such as one or more of the following: age, gender, height, weight, type of body build, and body fat percentage. Additionally or alternatively, data used to generate at least some of the feature values by the computer 686 may include various values describing an activity of the user while TH_(RBN) 683 of the user were taken. Optionally, data describing the activity is obtained by sensor 684. In one example, the sensor 684 comprises at least one of an accelerometer and a gyroscope, and the data describing the activity is indicative of at least one of the following: cadence, stride length, and/or type of movement (e.g., walking, running, rowing, cycling, etc.) In another example, the sensor 684 comprises a GPS receiver and/or some other sensor that may be used to determine the user's location. In this example, the data describing the activity may be indicative of one or more of the following: the speed of the user's movement, the distance of the user's movement, and/or changes in the user's elevation.

A person's baseline physiological signals, such as resting HR, respiration rate, or blood pressure may be indicative of the aerobic fitness of the person, and may provide useful information for calculation of an aerobic activity parameter. Thus, in some embodiments, the computer 686 may generate one or more feature values that are indicative of a baseline physiological signal of the user.

How a person's physiological signals change due to physical activity are indicative of the aerobic fitness of the person. Typically, the more fit an individual, the less dramatic the changes in the physiological signals for a certain type of activity. For example, a fit person's respiration rate will typically increase to a lesser extent after a few minutes of jogging compared to the increase in respiration that occurs to a less fit individual after performing the activity. To capture such aspects that may reflect on fitness, in some embodiments, the feature values generated by the computer 686 may include one or more feature values that reflect a change in the values of a physiological signal, before and after a certain extent of activity. For example, a feature value may be indicative of the change in the respiratory rate, change to the respiration volume, or respiration volume after conducting a certain activity (e.g., five minutes of moderate cycling). In another example, a feature value may be indicative of the change to the heart rate after running at a pace of 12 km/h for five minutes.

In other embodiments, the feature values generated by the computer 686 may include one or more feature values that are indicative of athletic performance of the user. For example, a feature value may be indicative of the time it took the user to complete a certain exercise such as running a mile as fast as the user is capable.

The model 687 is trained on data that includes previous TH_(RBN) of the user and/or other users. Training the model 687 typically involves generating samples based on the previous TH_(RBN) and corresponding labels indicative of values of the aerobic activity parameter when the previous TH_(RBN) were taken. For example, each sample may comprise feature values generated based on at least some of the previous TH_(RBN), and the sample's label represents the value of the aerobic activity parameter corresponding to when the at least some of the previous TH_(RBN) were taken.

In some embodiments, the samples used to train the model 687 include data pertaining to a diverse set of users comprising users of different genders, ages, body builds, and athletic abilities. Optionally, the samples used to train the model 687 include samples generated based on TH_(RBN) taken at different times of the day, while being at different locations, and/or while conducting different activities. In one example, at least some of the samples are generated based on TH_(RBN) taken in the morning and TH_(RBN) taken in the evening. In another example, at least some of the samples are generated based on TH_(RBN) of a user taken while being indoors, and TH_(RBN) of the user taken while being outdoors. In yet another example, at least some of the samples are generated based on TH_(RBN) taken while a user was sitting down, and TH_(RBN) taken while the user was walking, running, and/or engaging in physical exercise (e.g., dancing, biking, etc.). Additionally or alternatively, the samples used to train the model 687 may be generated based on TH_(RBN) taken while various environmental conditions persisted. For example, the samples include first and second samples generated based on TH_(RBN) taken while the environment had first and second temperatures, with the first temperature being at least 10° C. warmer than the second temperature. In another example, the samples include samples generated based on measurements taken while there were different extents of direct sunlight and/or different extents of wind blowing.

Various computational approaches may be utilized to train the model 687 based on the samples described above. In one example, a machine learning-based training algorithm may be utilized to train the model 687 based on the samples. Optionally, the model 687 includes parameters of at least one of the following types of models: a regression model, a neural network, a nearest neighbor model, a support vector machine, a support vector machine for regression, a naïve Bayes model, a Bayes network, and a decision tree.

In some embodiments, a deep learning algorithm may be used to train the model 687. In one example, the model 687 may include parameters describing multiple hidden layers of a neural network. In one embodiment, when TH_(RBN) include measurements of multiple pixels, the model 687 may include a convolution neural network (CNN). In one example, the CNN may be utilized to identify certain patterns in the thermal images, such as patterns of temperatures in the region of the exhale stream that may be indicative of respiratory activity, which involve aspects such as the location, direction, size, and/or shape of an exhale stream from the nose and/or mouth. In another example, calculating a value of an aerobic activity parameter may be done based on multiple, possibly successive, thermal measurements. Optionally, calculating values of the aerobic activity parameter based on thermal measurements may involve retaining state information that is based on previous measurements. Optionally, the model 687 may include parameters that describe an architecture that supports such a capability. In one example, the model 687 may include parameters of a recurrent neural network (RNN), which is a connectionist model that captures the dynamics of sequences of samples via cycles in the network's nodes. This enables RNNs to retain a state that can represent information from an arbitrarily long context window. In one example, the RNN may be implemented using a long short-term memory (LSTM) architecture. In another example, the RNN may be implemented using bidirectional recurrent neural network architecture (BRNN).

Monitoring a user over time can produce many observations indicative of the user's fitness. For example, the extent of increase in the user's respiration rate, change to respiration volume, and/or change in heart rate after moderate running of a few minutes, is indicative of the user's fitness, and can be measured multiple times. These multiple observations can be used to estimate the value of an aerobic activity parameter of the user such as VO₂ max (which is also indicative of the user's fitness) as follows. In one embodiment, the computer 686 calculates, based on TH_(RBN) 683, n≥1 values x₁ . . . x_(n), of observations of a parameter related to respiration such as the respiration rate, change to respiration rate, respiration volume, change to respiration volume, and the like. For example, x_(i) may be the increase to the respiration rate observed after moderate running for a period (e.g., five minutes). In another example, x_(i) may be the change to respiration volume and/or average respiration volume during a half hour of cycling.

The computer 686 may calculate an estimation of a value of the aerobic activity parameter (denoted θ*) utilizing one or more probability functions of the form P(X=x|θ), which is a conditional probability of a value of the parameter related to respiration given a value of the aerobic activity parameter is equal to θ. Optionally, the computer 686 performs at least one of the following in order to calculate θ* (the estimation value of the aerobic activity parameter): a maximum likelihood (ML) estimation, and a maximum a posteriori probability (MAP) estimation.

The one or more probability functions of the form P(X=x|θ) may be calculated based on data pertaining to a diverse set users comprising users of different genders, ages, body builds, and athletic abilities. Optionally, the data includes observations of a parameter related to respiration calculated based on TH_(RBN) of the users. In one embodiment, a probability function of the form P(X=x|θ) may be a table describing the probability of observing different values of x given a certain value of θ. For example, the table may describe an empirically observed probabilities for various increases in respiration (e.g., increases of 2, 4, 6, . . . , 40 breaths per minute) given different values of θ, such as VO₂ max=10, 15, 20, . . . , 75, 80 mL/(kg·min). In another embodiment, a probability function of the form P(X=x|θ) may be described by a model that includes parameters of the distribution, where the parameters may be set using various approaches such as regression and/or maximum entropy approaches. Optionally, the parameters of the probability function describe a continuous exponential distribution.

A user interface 689 may be utilized to present the aerobic activity parameter 688 and/or present an alert related to the aerobic activity parameter 688. In one example, user interface 689 may be used to alert the user responsive to an indication that the aerobic activity parameter has fallen below a threshold (e.g., when the rate of energy expenditure falls below a threshold) or when the aerobic activity parameter reaches a certain threshold (e.g., when the total energy expenditure during a session reaches a certain caloric goal). Optionally, the user interface 689 includes a display, such as the display of a smart phone, a smartwatch, or a head-mounted augmented reality display. Optionally, the user interface 689 includes a speaker, such as a speaker of a smart phone, a smartwatch, or a head-mounted augmented reality display, or a speaker of a pair of headphones or an earbud.

As discussed herein, thermal measurements indicative of an exhale stream may be used by a computer to calculate various respiratory parameters, aerobic activity parameters, and coaching indications. In order to produce a better signal regarding the user's respiratory activity, in some embodiments, the computer 686 (or the computer 696 discussed below) may utilize additional input sources (besides thermal cameras).

In some embodiment, the additional input sources may include one or more visible-light cameras that capture images indicative of respiratory activity. In one example, the additional input sources include at least one inward-facing head-mounted visible-light camera (e.g., the camera 682), which is configured to take images of a region on the mouth (IM_(M)) of the user. In this example, IM_(M) are indicative of whether the mouth is open or closed. In another example, the additional input sources include at least one inward-facing head-mounted visible-light camera configured to take images of a region on the nose (IM_(N)) of the user; in this example, IM_(N) are indicative of movement of the nose while the user inhales (in this example, the camera 682 may be configured to take images of the nose in addition to, or instead of, the images of the mouth). Optionally, calculating various values (e.g., breathing rate, an aerobic activity parameters, or a coaching indication) based on IM_(M) and/or IM_(N) involves generating feature values based on IM_(M) and/or IM_(N) and using them in the calculation of said values (e.g., in addition to feature values generated based on TH_(RBN)). For example, feature values generated based on IM_(M) and/or IM_(N) involve using various image processing techniques and represent various low-level image properties. Some examples of such features may include features generated using Gabor filters, local binary patterns and their derivatives, features generated using algorithms such as SIFT, SURF, and/or ORB, and features generated using PCA or LDA. Optionally, IM_(M) and/or IM_(N) may be used to identify different states of the user (e.g., open vs. closed mouth or movement of the nostrils), and the information regarding the different states may be used as input (e.g., feature values) when calculating parameters such as the breathing rate.

In other embodiments, the additional input sources may include one or more microphones configured to record sounds made by the user's respiration. For example, the one or more sensors may include microphones in right and/or left in-the-ear earbuds, and feature values may be generated based on audio signal analysis of the recordings from the earbuds and utilized to calculating parameters such as the breathing rate, to detect inhaling/exhaling events, etc. Optionally, such in-ear measurements are used to calculate the user's breathing rate while the user was walking or running in an environment having ambient noise level above 50 dBA.

Other examples or sensors that may be used as additional input sources include sensors physically that are coupled to a garment worn over the user's torso and comprises at least one of the following: a pressure sensor, a stretch sensor, an electromechanical sensor, and a radio receiver. Optionally, these sensors are configured to measure movements of the chest due to respiration activity of the user, and these measurements are utilized to calculate various parameters such as the breathing rate.

The additional input sources described above may serve, in some embodiments, as complementary data that enhance accuracy of respiratory signals detected based on TH_(RBN). For example, in some embodiments, exhaling air produces a stronger thermal signal than inhaling air. In these embodiments, detection of inhalation events can be assisted by images of the nostrils (which often show distinct movement when inhaling). In another example, there may be conditions in which exhaling may produce a relatively weak thermal signal, e.g., when exercising in warm environments in which the temperature of the exhaled air is close to the temperature in the environment. In such cases, additional data, such as data from sensors embedded in a garment or microphones in earbuds, may help and provide better indications of breathing.

The following is a description of another possible utilization of TH_(RBN), which involves virtual coaching based on respiration data. FIG. 37b illustrates an embodiment of an athletic coaching system. The system includes at least one CAM (as described above) that is used to measure TH_(RBN) 693 and a computer 696. Some embodiments of the system may optionally include additional elements, such as the frame 680, a head-mounted inward-facing video camera 692, a sensor 694, and a user interface 699.

The computer 696 is configured, in some embodiments to: receive measurements of movements (M_(move) 695) involving the user; generate, based on TH_(RBN) 693 and M_(move) 695, a coaching indication 698; and present, via a user interface 699, the coaching indication 698 to the user. Various virtual coaching applications may be realized by analyzing TH_(RBN) 693 and M_(move) 695, and providing the user with insights and/or instructions based on the analysis. These insights and/or instructions may assist to improve the user's athletic performance in various ways.

One type of coaching application built on the system illustrated in FIG. 37b provides insights and/or instructions to a user performing an athletic activity that involves an aerobic exercise with repetitive motions such as running, rowing, or cycling. In one embodiment, the computer 696 generates the coaching indication 698, which is indicative of a change the user should make to one or more of the following: cadence of movements, stride length (if the user is running), breathing rate, breathing type (mouth or nasal), and duration of exhales. Optionally, responsive to a determination that the change is needed, the computer 696 provides, via the user interface 699, an indication to the user of this fact. For example, the user interface 699 may include a speaker (e.g., in earbuds) and the computer 696 generates an audio indication (e.g., a certain sound effect such as beeping at a certain frequency and/or speech conveying the coaching indication 698). In another example, the user interface may include a display and the coaching indication may be provided via visual cues (e.g., text, an image, or a light flashing at a certain frequency). The following are various examples of computations that may be performed by the computer 696 in order to generate the coaching indication 698.

In one embodiment, the computer 696 calculates the breathing rate of the user based on TH_(RBN) 693 and then checks if it is in a desired range. Responsive to the breathing rate being below a first threshold, the computer 696 includes in the coaching indication 698, an instruction to increase the breathing rate. Additionally or alternatively, responsive to the breathing rate being above a second threshold (which is higher than the first threshold), the computer includes in the coaching indication 698 an instruction to decrease the breathing rate. Optionally, the first and/or second thresholds are calculated based on M_(move) 695. For example, the first threshold (minimal desired breathing rate) and/or the second threshold (maximal desired breathing rate) are set according to the level of activity of the user. Optionally, “level of activity” may refer to one or more of the following: the speed of the user (e.g., when running or cycling), the cadence of the user's movement, a value of an aerobic activity parameter of the user (e.g., VO₂ or EE).

In another embodiment, the computer 696 calculates a value indicative of the cadence of the user based on M_(move) 695. For example, the computer 696 may identify cyclic signals indicating movement such as pedaling, rowing, or strides. Optionally, the computer 696 utilizes a machine learning model to calculate the cadence based on M_(move) 695, where the model is trained based on M_(move) of other users. Optionally, responsive to the cadence being below a first threshold, the computer 696 includes in the coaching indication 698 an instruction to increase the cadence. Additionally or alternatively, responsive to the cadence being above a second threshold, the computer 696 includes in the coaching indication 698 an instruction to decrease the cadence. Optionally, the first and/or second thresholds are calculated according to TH_(RBN) 693. For example, the first and/or second thresholds may correspond to a desired cadence that is appropriate for the breathing rate of the user, as determined based on TH_(RBN) 693.

In yet another example, the computer 696 calculates a value indicative of exhale durations of the user based on TH_(RBN) 693. Optionally, the computer 696 includes in the coaching indication 698 an instruction to increase the exhale durations responsive to determining that the exhale durations are below a threshold. Optionally, the threshold is calculated based on at least one of M_(move) 695 and TH_(RBN) 693. For example, the threshold may be set according to a predetermined function that assigns a minimal desired duration of exhales based on the cadence or speed of the user (e.g., as determined based on M_(move) 695) and/or based on the breathing rate of the user (e.g., as determined based on TH_(RBN) 693).

In still another embodiment, the computer 696 detects, based on TH_(RBN) 693, whether the user is breathing through the mouth. Responsive to detecting that the user is breathing through the mouth, the computer 696 includes in the coaching indication 698 an instruction to the user to breathe through the nose.

The computer 696 may utilize a machine learning model 697 to generate the coaching indication 698. In some embodiments, the computer generates feature values based on TH_(RBN) 693 and/or M_(move) 695. For example, the feature values may include one or more of the feature values described above which are generated based on TH_(RBN) 683 and/or measurements of the sensor 684 and are used to estimate the aerobic activity parameter 688. Optionally, the computer 696 utilizes the model 697 to calculate, based on the feature values generated based on TH_(RBN) 693 and/or M_(move) 695, a value indicative of whether the change is needed and/or what change in the user's activity should be indicated in the coaching indication 698.

The model 697 may be generated based on data comprising previously taken TH_(RBN) and M_(move) of the user and/or other users and indications of appropriate coaching instructions (and whether coaching instructions are needed) corresponding to the time previously taken TH_(RBN) and M_(move) were taken. For example, the previously taken TH_(RBN) and M_(move) may be used to generate samples; each sample comprising feature values generated based on TH_(RBN) and M_(move) taken during a certain period (the same type of feature values generate by the computer 696, as described above). The indications on appropriate coaching instructions may be used to create labels for the samples. In one example, the coaching instructions are provided by a human annotator (e.g., a human coach) that reviews the data and determines whether changes could be made to improve the athletic performance. In another example, the coaching instructions are provided by an expert system (e.g., a rule based system such as a decision tree), which is designed for this purpose.

In some embodiments, M_(move) 695 are generated by a sensor 694, which may represent herein one or more of various types of sensors. In one embodiment, the sensor 694 is an accelerometer and/or gyroscope in a device carried or worn by the user. For example, the sensor 694 may be a movement sensor in a smartwatch or smart glasses worn by the user or a movement sensor in a smartphone carried by the user. Optionally, analysis of measurements of the sensor 694 provides information about one or more of the following: the types of movements the user is making (e.g., running, cycling, or rowing), the cadence of the user (e.g., number of steps per minute, number of revolutions per minute in cycling, or the number of strokes per minute), and/or the speed of the user. In another embodiment, the sensor 694 is a location identifying sensor, such as a GPS receiver. Optionally, analysis of measurements of the sensor 694 provides information on the speed of the user, the elevation and/or distance traveled, etc. In some embodiments, M_(move) 695 may include information obtained from multiple movement sensors. In one example, information about the speed and/or distance traveled by the user, coupled with information about the cadence, is used in order to determine the length of the user's strides.

Another type of coaching application that may utilize TH_(RBN) 693 and M_(move) 695 provides the user with breathing cues (e.g., a breathing pacer application) in order to assist the user to breathe at a desired pace while conducting athletic activity. In one embodiment, the computer 696 calculates a target breathing rate based on data comprising at least one of TH_(RBN) 693 and M_(move) 695, and includes in the coaching indication breathing cues that correspond to the target breathing rate. Optionally, the computer 696 receives a value indicative of the heart rate (HR) of the user and uses HR to calculate the target breathing rate (in addition to utilizing at least one of TH_(RBN) 693 and M_(move) 695). In one example, M_(move) 695 is utilized to calculate a value indicative of the speed of the user and/or the cadence of the user, and the computer 696 utilizes a predetermined function to select for the user the target breathing rate, based on the speed and/or the cadence. In another example, a current breathing rate of the user, which is calculated based on TH_(RBN) 693, is used to select a target breathing rate that will match the cadence of the user (e.g., which is determined based on M_(move) 695). In still another example, TH_(RBN) 693 and M_(move) 695 are used as input to a function that calculates the target breathing rate. For example, the computer 696 may generate feature values (e.g., as discussed above with respect to the coaching indication regarding an instruction to change an aspect of the user's activity) and utilize a certain model to calculate, based on these feature values, the target breathing rate. Optionally, the certain model is generated based on data comprising previously taken TH_(RBN) and M_(move) of the user and/or other users and indications of the appropriate breathing rate as determined by an expert (e.g., a human or an expert system). The various computational approaches described herein with respect to detecting a physiological response may be employed in order to calculate the target breathing rate (e.g., comparison to threshold, reference time series, and/or machine learning approaches described herein).

In one embodiment, the computer 696 calculates a current breathing rate based on TH_(RBN) 693 and compares the current breathing rate to first and second thresholds, where the first threshold is below the target breathing rate and second threshold is above the target breathing rate. Responsive to the current breathing rate being below the first threshold or above the second threshold, the computer 696 instructs the user interface 699 to start providing the breathing cues or to increase intensity of provided breathing cues. Optionally, responsive to the current breathing rate being above the first threshold and below the second threshold, for at least a certain duration, the computer 696 instructs the user interface 699 to cease from providing the breathing cues or to provide weaker breathing cues.

The breathing cues may be provided in various ways. In one example, the user interface 699 includes a speaker (e.g., in an earbud) and the breathing cues comprise auditory cues that have a frequency that corresponds to the target breathing rate (e.g., a beeping sound at the frequency or a music that has an underlying beat at the frequency). FIG. 37c illustrates a cycler who receives breathing cues via an earbud, which correspond to the target breathing rate. In another example, the user interface 699 includes a display (e.g., a display of augmented reality smart glasses, and the breathing cues comprise visual cues that have a frequency that corresponds to the target breathing rate (e.g., a flashing light or icon that changes its size at a frequency that corresponds to the target breathing rate).

Yet another type of coaching application that may utilize TH_(RBN) 693 and M_(move) 695 a coaching indication indicative synchronization of a breathing pattern of the user with a sequence of movements of the user. Optionally, the coaching indication 698 may be indicative of whether the breathing is synchronized with a sequence of movements (i.e., indicate to the user whether the user is breathing correctly when performing the sequence of movements). Additionally or alternatively, the coaching indication 698 may provide cues of the correct breathing pattern corresponding to the sequence of movements (i.e., provide cues that indicate to the user a synchronized breathing pattern). In one embodiment, the computer 696 provides the user, via the user interface 699, an indication indicative of whether the user's breathing is synchronized with the sequence of movements. Additionally or alternatively, the computer 696 determine whether the user did not breathe in an appropriate pattern while performing a sequences of movements. Responsive to determining that the user did not breathe in the appropriate pattern, the computer 696 notifies the user of this fact via a user interface 699.

A “correct” breathing pattern refers to a breathing pattern that is considered appropriate for the sequence of movements, and thus may be considered synchronized with the sequence of movements. Optionally, determining a breathing pattern that is correct for a sequence of movements may be done based on expert knowledge (e.g., coaches, experts in athletics and physiology, etc.) Additionally or alternatively, correct breathing patterns for a sequence of movements may be learned from observations. For example, performance of one or more users may be monitored while they breathe in various patterns while performing a certain sequence of movements, and the optimal breathing pattern (i.e., the breathing pattern that is synchronized with the certain sequence) may be determined based on detecting a breathing pattern for which the performance is maximized (e.g., farthest/most accurate driver hit).

The sequence of movements performed by the user may be, in some embodiments, sequences involved in performing a specific operation, such as swinging a bat, a racket or a golf club, lifting weights, performing a move in yoga, etc. In such cases, various sensors may be utilized in order to obtain M_(move) 695, which provide indications of the type of movements the user is performing and/or how the user is manipulates objects (such as a bat, a racket, a golf club, a barbell, etc.). In some embodiments, the sensor 694 is a camera that takes images of the user, the user's limbs, and/or objects held by the user. In one example, the sensor 694 is an outward-facing head-mounted camera (e.g., a camera pointed outwards that is coupled to a frame worn on the user's head). In another example, the sensor 694 is an external camera, such as a camera in a laptop, smart TV, or a webcam. Optionally, the computer 696 performs image analysis of M_(move) 695 that includes images taken by the sensor 694 in order to identify various movements of the user.

In some embodiments, the sensor 694 may include at least one of LiDAR system and a RADAR system. Optionally, the computer 696 analyzes M_(move) 695 in order to identify movements of the user's limbs, changes to the user's pose, and/or the location of an object held by the user (e.g., a barbell, racket, golf club, etc.)

The following are examples of various sequences of movements and coaching indications that may be generated for them based on TH_(RBN) 693 and M_(move) 695.

In one embodiment, a sequence of movements of the user corresponds to a pressing motion of weights or a barbell, and the coaching indication 698 indicates to inhale in the concentric phase of the press and exhale in the eccentric phase of the press. In one example, the sensor 694 is a movement sensor (e.g., an accelerometer embedded in a garment worn by the user) and the computer 696 analyzes M_(move) 695 to identify different movements involved in the pressing motion. In another example, the sensor 694 is an outward-facing head-mounted camera or a camera external to the user, and M_(move) 695 include images of the user and/or of the weights or barbell. In this example, the computer 696 may utilize image analysis of M_(move) 695 in order to identify different movements involved in the pressing motion. Optionally, the coaching indication 698 is provided to the user while the user performs the sequence of movements, such that when the computer 696 recognizes that the user is about push the weights or barbell, or starts to push (initiating the concentric phase), the user is instructed, in the coaching indication 698, to exhale.

In another embodiment, a sequence of movements of the user corresponds to swinging a racket in order to hit a ball with the racket (e.g., while playing tennis), and the coaching indication 698 indicates to exhale while hitting the ball. In one example, the sensor 694 is a movement sensor (e.g., an accelerometer) on the user's body, and the computer 696 analyzes M_(move) 695 to identify movements that characterize a swinging motion. In another example, the sensor 694 comprises at least one of a LiDAR system and a RADAR system, and the computer 696 analyzes M_(move) 695 to determine the location of the arms and/or the racket relative to the user's body in order to identify the swinging motion. Optionally, the coaching indication 698 is provided to the user while the user performs the sequence of movements, such that when the computer 696 recognizes that the user is about swing the racket, or starts to starts to swing the racket, the user is instructed, in the coaching indication 698, to exhale.

In yet another embodiment, a sequence of movements of the user corresponds to making a drive shot in golf, and the coaching indication 698 indicates to inhale during the backswing and exhale again on the downswing. Optionally, the coaching indication 698 also indicates to exhale at address. Optionally, the coaching indication 698 is provided to the user while the user performs the sequence of movements, such that when the computer 696 recognizes that the user is about to drive the shot (e.g., based on characteristic movements in the address), or starts the drive shot (e.g., by starting the backswing), the user is instructed, in the coaching indication 698, to exhale. FIG. 37d illustrates a user receiving coaching instructions while hitting a drive in golf; the figure illustrates the user receiving instructions (e.g., via an earbud) to inhale on the backswing and exhale of the downswing.

In still another embodiment, the computer 696: (i) receives from a fitness app (also known as a personal trainer app) an indication that the user should exhale while making a movement, (ii) determines, based on m_(move) 695, when the user is making the movement, and (iii) determines, based on TH_(RBN) 693, whether the user exhaled while making the movement. Optionally, the computer 696 commands the user interface 699 to (i) play a positive feedback in response to determining that the user managed to exhale while making the physical effort, and/or (ii) play an alert and/or an explanation why the user should try next time to exhale while making the physical effort in response to determining that the user did not exhale while making the physical effort. FIG. 28a illustrates a fitness app running on smartphone 196, which instructs the user to exhale while bending down. CAM coupled to eyeglasses frame 181 measures the user breathing and is utilized by the fitness app that helps the user to exhale correctly. FIG. 28b illustrates inhaling while straightening up.

There are various ways in which the computer 696 may generate a coaching indication that is indicative of synchronization of a breathing pattern of the user with a sequence of movements of the user. In some embodiments, generating the coaching indication 698 involves identifying a breathing pattern based on TH_(RBN) 693 and/or the sequence of movements based on M_(move) 695. Additionally or alternatively, a machine learning model may be used to calculate, based on TH_(RBN) 693 and M_(move) 695, a value indicative of an extent to which the breathing pattern of the user is synchronized with the sequence of movements.

In some embodiments, a breathing pattern may refer to a description of characteristics of the user's breathes during a certain period of time. Optionally, the breathing pattern is determined by identifying, based on TH_(RBN) 693, times at which the user inhaled or exhaled and/or by calculating, based on TH_(RBN) 693, one or more of the various respiratory parameters described herein. Optionally, a breathing pattern may describe one or more of the following values: times at which the user inhaled, times at which the user exhaled, durations of inhales, durations of exhales, respiration volume (or changes to the respiration volume), indications of whether the user exhaled and/or inhaled from the mouth, and indications of whether the user exhaled and/or inhaled from the nose. Optionally, the values comprised in a breathing pattern include corresponding temporal values. For example, a breathing pattern may include the following: at time t=−0 inhaling, at time t=1.5 exhaling, at time t=3 inhaling, . . . , etc. Additionally or alternatively, a breathing pattern may include qualitative descriptors of respiration (determined based on TH_(RBN) 693). For example, a breathing pattern may include the following descriptors: a regular inhaling followed by a short bursty exhaling (e.g., when hitting a ball).

In some embodiments, a sequence of movements of the user may refer to values describing movement of the user's body (changing location in the 3D space) and/or changes to pose and/or orientation of limbs. Optionally, the sequence of movements may be represented using descriptors that represent specific movements that are identified based on M_(move) 695. For example, the sequence of movements describing a drive shot in golf may include descriptors such as: getting into position (address), a backswing, and a downswing. Optionally, the descriptors of movements in a sequence of movements may have associated temporal values describing properties such as when each of the movements started and/or how long each of the movements lasted.

In one embodiment, identifying a certain movement, from among the sequence of movements, is done using a machine learning-based model. M_(move) 695 (or a portion thereof, e.g., a segment lasting a second) are converted into feature values representing values of M_(move) (e.g., values of an accelerometer, low-level image features, etc.), using approaches described herein and/or approaches known in the art. A model is utilized to calculate, based on the feature values, a value indicative of whether the user performed the certain movement. Optionally, the model is trained on samples of one or more users, each comprising feature values generated based on M_(move) of a user taken while said user performed the certain movement. Optionally, the model is trained on samples of one or more users, each comprising feature values generated based on M_(move) of a user taken while said user did not perform the certain movement.

In one embodiment, identifying a certain movement, from among the sequence of movements, is done using similarity to reference M_(move) taken while a certain user performed the certain movement. M_(move) 695 (or a portion thereof, e.g., a segment lasting a second), is compared to the reference M_(move) and if the similarity reaches a threshold, the user is considered to have performed the certain movement while M_(move) 695 (or the portion thereof) were taken. In one example, the segments of M_(move) being compared are treated as time series data, and one or more of the methods referenced herein with respect to determining similarity of time series are used to determine the similarity. In another example, the segments of M_(move) being compared may be represented as points in a high dimensional space, and a distance function such as the Euclidian distance or some other distance function is used find the distance between the points. The threshold, to which the similarity is compared, may be determined experimentally and selected in order to achieve a desirable balance between specificity and sensitivity of identifications of the certain movement.

In order to determine to what extent the sequence of movements (determined based on M_(move) 695) is synchronized with the breathing pattern (determined based on TH_(RBN) 693) the computer 696 may align the sequence of movements and breathing pattern (e.g., by using temporal information associated with both). This alignment may be done in different ways. In one example, the alignment determines which respiratory actions were performed when different movements of the sequence of movements were performed. In this example, the computer 696 may utilized the alignment to determine whether the respiratory actions correspond to one or more predetermined breathing patterns appropriate for the certain movement sequence.

In another embodiment, feature values are generated based on the sequence of movements and the breathing pattern. For example, some of the feature values may describe which movements were performed, their relative order, and timing. Additionally some feature values may describe which respiratory activities were performed, their order/timing/duration, and other related properties described above. A model is used to calculate, based on the feature values, a value indicative of the extent to the breathing pattern is synchronized with the sequence of movements. Optionally, the model is trained based samples generated from M_(move) and TH_(RBN) of one or more users, which include samples generated based on M_(move) and TH_(RBN) taken while the sequence of movements was performed and a user was breathing in a breathing pattern that was synchronized with the sequence of movements. Additionally, the samples used to train the model may include samples generated based on M_(move) and TH_(RBN) taken while the sequence of movements was performed and a user was not breathing in a breathing pattern that was synchronized with the sequence of movements. Optionally, a breathing pattern is considered not to be synchronized with a sequence of movements if the extent of the synchronization between the two is below a predetermined threshold (and considered synchronized otherwise).

In yet another embodiment, a unified sequence is created from the breathing pattern and the sequence of movements, which describes both movements and respiration activities. For example, the sequence of movements and the breathing pattern may be merged to a single sequence using temporal data. This unified sequence may then be evaluated to determine whether it corresponds to a breathing pattern that is synchronized to a sequence of movements based on similarity to a reference unified sequence and/or a machine learning-based model trained on samples generated based on unified sequences that are generated based on M_(move) and TH_(RBN) taken while the sequence of movements was performed and a user was breathing in a breathing pattern that was synchronized with the sequence of movements.

In some embodiments, determining whether a breathing pattern is synchronized with a sequence of movements of the user is done using a machine learning-based model. The computer 696 generates feature values based on TH_(RBN) 693 (e.g., one or more feature values of types described herein which are used to calculate a respiratory parameter) and/or based on M_(move) 695 (e.g., feature values described above which are used to identify certain movements). The computer 696 utilizes the machine learning-based model to calculate, based on the feature values, a value indicative of whether the breathing pattern was synchronized with the sequence of movements. Optionally, the model was trained based on data comprising: a first set of previous TH_(RBN) and M_(move) of one or more users, taken while performing the sequence of movements and breathing in a pattern that is synchronized with the sequence of movements, and a second set of previous TH_(RBN) and M_(move) of the one or more users taken while performing the sequence of movements and breathing in a pattern that is not synchronized with the sequence of movements.

FIG. 38 illustrates one embodiment of a system configured to provide neurofeedback (based on measurements of thermal camera 720) and/or breathing biofeedback (based on measurements of at least one of thermal cameras 723, 725, 727 and 729). Thermal camera 720 takes thermal measurements of a region on the forehead 721, thermal cameras 723 and 725 take thermal measurements of regions on the right and left sides of the upper lip, respectively, and thermal cameras 727 and 729 take thermal measurements of regions on the user's mouth and/or volumes protruding out of the user's mouth. The thermal cameras are physically coupled to a frame 731 that may be part of an augmented-realty system in which the visual feedback of the breathing biofeedback and/or neurofeedback is presented to the user via UI 732. The system may control the breathing biofeedback and/or neurofeedback session based on measurements taken by additional sensors, such as (i) sensor 722, which may be an outward-facing thermal camera that measures the intensity of infrared radiation directed at the face, and (ii) thermal cameras 724 and 726 that measure regions on the right and left periorbital areas, respectively.

In one embodiment, a system configured to provide a breathing biofeedback session for a user includes at least one inward-facing head-mounted thermal camera (CAM) and a user interface (UI). The at least one CAM takes thermal measurements of a region below the nostrils (TH_(ROI)), and TH_(ROI) are indicative of the exhale stream. The UI provides feedback, calculated based on TH_(ROI), as part of a breathing biofeedback session for the user. Optionally, the breathing biofeedback system may include additional elements such as a frame, a computer, additional sensors, and/or thermal cameras as described below.

The at least one CAM may have various configurations. In a first example, each of the at least one CAM is located less than 15 cm from the user's face and above the user's upper lip, and does not occlude any of the user's mouth and nostrils. Optionally, TH_(ROI) include thermal measurements of at least first and second regions below right and left nostrils of the user. Optionally, the at least one CAM consists of a single CAM.

In a second example, the system further includes a frame worn on the user's head. TH_(ROI) include thermal measurements of first and second regions below right and left nostrils (TH_(ROI1) and TH_(ROI2), respectively) of the user. The at least one CAM includes first and second thermal cameras for taking TH_(ROI1) and TH_(ROI2), respectively, which are located less than 15 cm from the user's face and above the nostrils. The first thermal camera is physically coupled to the right half of the frame and captures the exhale stream from the right nostril better than it captures the exhale stream from the left nostril, and the second thermal camera is physically coupled to the left half of the frame and captures the exhale stream from the left nostril better than it captures the exhale stream from the right nostril.

In a third example, TH_(ROI) include thermal measurements of first, second and third regions on the user's face, which are indicative of exhale streams from the right nostril, the left nostril, and the mouth, respectively. The first and second regions are below the right and left nostrils, respectively, and the third region includes the mouth and/or a volume protruding out of the mouth.

The UI provides the feedback for the user during the breathing biofeedback session. The UI may also receive instructions from the user (e.g., verbal commands and/or menu selections) to control the session parameters, such session duration, goal, and type of game to be played. The UI may include different types of hardware in different embodiments. Optionally, the UI includes a display that presents the user with video and/or 3D images, and/or a speaker that plays audio. Optionally, the UI is part of a device carried by the user. Optionally, the UI is part of a HMS to which the at least one CAM is coupled. Some examples of displays that may be used in some embodiments include a screen of a handheld device (e.g., a screen of a smartphone or a smartwatch), a screen of a head-mounted device (e.g., a screen of an augmented reality system or a virtual reality system), and a retinal display. In one embodiment, the UI may provide tactile feedback to the user (e.g., vibrations).

In some embodiments, at least some of the feedback presented to the user via the UI is intended to indicate to the user whether, and optionally to what extent, the user's breathing (as determined based on TH_(ROI)) is progressing towards a target pattern. The feedback may be designed to guide the user to breathe at his/her resonant frequency, which maximize amplitude of respiratory sinus arrhythmia and is in the range of 4.5 to 7.0 breaths/min.

The feedback may indicate the user's progress towards the target in different ways, which may involve visual indications, audio indications, and/or tactile indications. In one embodiment, the user is provided with a visual cue indicating the extent of the user's progress. For example, an object may change states and/or locations based on how close the user is to the target, such as an image of a car that moves forward as the user advances towards the target, and backwards if the user regresses. In one example, the feedback may include an audio-visual video of a fish that swims to the left when the exhale becomes smoother and stops swimming or even swims to the right when the exhale becomes less smooth. In another embodiment, the user is provided with an audio cue indicating the extent of the user's progress. For example, music played to the user may change its volume, tune, tone, and/or tempo based on whether the user is advancing towards the target or regressing from it, and/or different music pieces may be played when the user is at different rates of progression. In still another embodiment, the user is provided with a tactile cue indicating the extent of the user's progress. For example, a device worn and/or carried by the user may vibrate at different frequencies and/or at different strengths based on how far the user is from a goal of the session.

Breathing biofeedback requires closing the feedback loop on a signal that changes fast enough. Smoothness of the exhale stream, the shape, and/or the BRV have components that change at frequency above 2 Hz, which may be fast enough to act as the parameter on which the breathing biofeedback loop is closed. The feedback may be calculated and presented to the user at frequencies higher than 1 Hz, 2 Hz, 5 Hz, 10 Hz, 20 Hz and/or 40 Hz (which are all higher than the user's breathing rate).

The computer calculates, based on TH_(ROI), a characteristic of the user's breathing, and generates the feedback based on the characteristic. Some breathing characteristics may be difficult to control, and often people are not even aware of them. However, breathing biofeedback can help the user achieve awareness and/or gain control over his/her breathing, and as a result improve the user's state.

One characteristic of the breathing, which the computer may take into account when controlling the breathing biofeedback session, is the smoothness of the exhale stream. Optionally, the smoothness of the exhale stream refers to a mathematical property of sets of values that include values of TH_(ROI) taken over a period of time (e.g., values in a window that includes a portion of a breath, or even one or more breaths). The smoothness may be considered a property of graphs of the sets of values, and may represent how much of a variance there is in these values when compared to an average trend line that corresponds to the breathing. As discussed above, the smoothness may be calculated in various ways such as using Fourier transform and/or measuring a fit to a low order polynomial.

In one embodiment, the feedback is indicative of similarity between current smoothness of the exhale stream and target smoothness of the exhale stream. The current smoothness is calculated in real-time based on TH_(ROI), and the target smoothness is calculated based on previous TH_(ROI) of the user taken while the user was in a state considered better than the user's state while starting the breathing biofeedback session. Optionally, the similarity may be formulated as the distance between the current smoothness and the target smoothness.

In one embodiment, the feedback is indicative of at least one of the following: whether the smoothness is above or below a predetermined threshold, and whether the smoothness has increased or decreased since a previous feedback that was indicative of the smoothness. Optionally, the smoothness is calculated at frequency≥4 Hz, and the delay from detecting a change in the smoothness to updating the feedback provided to the user is ≤0.5 second. As another option, the feedback may be indicative of whether the smoothness is above or below the predetermined threshold, and the user interface may update the feedback provided to the user at a rate≥2 Hz.

Another characteristic of the breathing, which the computer may take into account when controlling the breathing biofeedback session, is the shape of the exhale stream (SHAPE). Optionally, the SHAPE is described by one or more parameters that represent a 3D shape that bounds the exhale stream that flows from one or both of the nostrils. Optionally, the feedback is indicative of whether the SHAPE matches a predetermined shape, and/or whether the SHAPE has become more similar or less similar to the certain shape since a previous feedback that was indicative of the SHAPE. In one embodiment, the feedback is indicative of similarity between current shape of the exhale stream (SHAPE) and target SHAPE, wherein the current SHAPE is calculated in real-time based on TH_(ROI), and the target SHAPE is calculated based on at least one of the following: (i) previous TH_(ROI) of the user taken while the user was in a state considered better than the user's state while starting the breathing biofeedback session, and (ii) TH_(ROI) of other users taken while the other users were in a state considered better than the user's state while starting the breathing biofeedback session.

Another characteristic of the breathing, which the computer may take into account when controlling the breathing biofeedback session, is the breathing rate variability (BRV), which is indicative of the variations between consecutive breathes. Optionally, the feedback may be indicative of similarity between current breathing rate variability (BRV) and a target BRV, wherein the current BRV is calculated in real-time based on TH_(ROI), and the target BRV is calculated based on previous TH_(ROI) of the user taken while the user was in a state considered better than the user's state while starting the breathing biofeedback session. Additionally or alternatively, the feedback may be indicative of whether the BRV is above or below a predetermined threshold, and/or whether a predetermined component of the BRV has increased or decreased since a previous feedback that was indicative of the BRV.

Similarly to how heart rate variability (HRV) is calculated, there are various computational approaches known in the art that may be used to calculate the BRV based on TH_(ROI). In one embodiment, calculating the BRV involves identifying matching events in consecutive breaths (such as start exhaling, exhale peak, and/or inhale peak), and analyzing the variability between these matching events. In another embodiment, the user's breathing is represented as time series data from which low frequency and high frequency components of the integrated power spectrum within the time series signal are extracted using Fast Fourier Transform (FFT). A ratio of the low and high frequency of the integrated power spectrum within these components is computed and analysis of the dynamics of this ratio over time is used to estimate the BRV. In still another embodiment, the BRV may be determined using a machine learning-based model. The model may be trained on samples, each including feature values generated based on TH_(ROI) taken during a certain period and a label indicative of the BRV during the certain period.

In some embodiments, the computer calculates a value indicative of similarity between a current TH_(ROI) pattern and a previous TH_(ROI) pattern of the user taken while the user was in a target state, and generates the feedback based on the similarity. Examples of TH_(ROI) patterns include at least one of: a spatial pattern (e.g., a pattern in a thermal image received from a FPA sensor), a pattern in the time domain (e.g., a pattern detected in a time series of the thermal measurements), and a pattern in the frequency domain (e.g., a pattern detected in a Fourier transform of the thermal measurements).

Biofeedback sessions may have different target states in different embodiments. Generally, the purpose of a session is to bring the user's state during the biofeedback session (the “present state”) to become more similar to a target state. In one embodiment, while the user was in the target state, one or more of the following were true: the user was healthier compared to the present state, the user was more relaxed compared to the present state, a stress level of the user was below a threshold, and the user was more concentrated compared to the present state. Additionally, the computer may receive an indication of a period during which the user was in the target state based on a report made by the user (the previous TH_(ROI) pattern comprises TH_(ROI) taken during the period), measurements of the user with a sensor other than CAM, semantic analysis of text written by the user, and/or analysis of the user's speech.

In another embodiment, the computer calculates a value indicative of similarity between current TH_(ROI) and previous TH_(ROI) of the user taken while the user was in a target state, and generates the feedback based on the similarity. The similarity may be calculated by comparing (i) a current value of a characteristic of the user's breathing, calculated based on TH_(ROI), to (ii) a target value of the characteristic of the user's breathing, calculated based on the previous TH_(ROI). Here, the feedback may be indicative of whether the current value of the characteristic of the user's breathing has become more similar or less similar to the target value of the characteristic of the user's breathing since a previous (related) feedback.

In still another embodiment, the computer compares a current set comprising feature values generated based on TH_(ROI) to a target set comprising feature values generated based on previous TH_(ROI) of the user, where the feature values are indicative of values of respiratory parameter(s).

In some embodiments, the system configured to provide a breathing biofeedback session receives indications of when the user is in the target state. Given such indications, the system may collect TH_(ROI) taken during these times and utilize them in biofeedback sessions to steer the user towards the desired target (these collected TH_(ROI) may be considered as the previous TH_(ROI) mentioned above). There are various sources for the indications of when the user is in the certain target state. In one example, the user may report when he/she is in such a state (e.g., through an “app” or a comment made to a software agent). In another example, measurements of the user with one or more sensors other than CAM may provide indications that the user is in a certain physiological and/or emotional state that corresponds to the certain target state. In still another example, an indication of a period of time in which the user was in a certain target state may be derived from analysis of communications of the user, such as using semantic analysis of text written by the user, and/or analysis of the user's speech.

In some embodiments, the computer may utilize a machine learning-based model to determine whether the session is successful (or is expected to be) and/or to determine the user's progress in the breathing biofeedback session at a given time (e.g., the rate of improvement the user is displaying at that time and/or how close the user is to the session's target). Optionally, the computer generates feature values based on TH_(ROI) (e.g., values of TH_(ROI) and/or statistics of TH_(ROI) taken over different periods during the session), and utilizes the model to calculate a value indicative of the progress and/or session success. Optionally, the model is trained on samples comprising feature values based on previously taken TH_(ROI) and labels indicative of the success of the session and/or progress at the time those TH_(ROI) were taken. Optionally, the samples may be generated based on previously taken TH_(ROI) of the user. Additionally or alternatively, the samples may be generated based on previously taken TH_(ROI) of other users. Optionally, the samples include samples generated based on TH_(ROI) taken on different days, and/or while the measured user was in different situations.

The following method for providing a breathing biofeedback session may be used, in some embodiments, by systems modeled according to FIG. 38. The steps described below may be performed by running a computer program having instructions for implementing the method. Optionally, the instructions may be stored on a computer-readable medium, which may optionally be a non-transitory computer-readable medium. In response to execution by a system including a processor and memory, the instructions cause the system to perform the following steps: In Step 1, taking thermal measurements of a region below the nostrils (TH_(ROI)) of a user using at least one CAM worn on the user's head; TH_(ROI) are indicative of the exhale stream. In Step 2, taking target TH_(ROI) (TARGET) when the user is in a desired state, such as relaxed, healthy, happy, energized, and/or in a state of elevated concentration. In Step 3, taking current TH_(ROI) (CURRENT) of the user. And in Step 4, providing the user with real-time feedback indicative of similarity between TARGET and CURRENT.

Generating the feedback may involve various calculations in different embodiments. For example, the method may include one or more of the following steps: (i) calculating target smoothness of the exhale stream based on TARGET and calculating current smoothness of the exhale stream based on CURRENT. Optionally, the feedback is indicative of similarity between the target smoothness and the current smoothness, (ii) calculating target shape of the exhale stream (SHAPE) based on TARGET and calculating current SHAPE based on CURRENT. Optionally, the feedback is indicative of similarity between the current SHAPE and the target SHAPE, and/or (iii) calculating target breathing rate variability (BRV) based on TARGET and calculating current BRV based on CURRENT. Optionally, BRV is indicative of variations between consecutive breathes, and the feedback is indicative of similarity between the current BRV and the target BRV.

In one embodiment, a system configured to select a state of a user includes at least one CAM and a computer. Each of the at least one CAM is worn on the user's head and takes thermal measurements of at least three regions below the nostrils (TH_(S)) of the user; wherein TH_(S) are indicative of shape of the exhale stream (SHAPE). The computer (i) generates feature values based on TH_(S), where the feature values are indicative of the SHAPE, and (ii) utilize a model to select the state of the user, from among potential states of the user, based on the feature values. Optionally, the model is utilized to calculate a value based on the feature values. In one example, the calculated value is indicative of which state the user is in, and the computer may calculate probabilities that the user is in each of the potential states, and select the state for which the probability is highest. In another example, the calculated value is an output of a classifier (e.g., a neural network-based classifier), which is indicative of the state the user is in.

In order for TH_(S) to be indicative of the SHAPE, the at least one CAM needs to capture at least three regions from which the shape can be inferred. In a first example, the sensing elements of the at least one CAM include: (i) at least three vertical sensing elements pointed at different vertical positions below the nostrils where the exhale stream is expected to flow, and/or (ii) at least three horizontal sensing elements pointed at different horizontal positions below the nostrils where the exhale stream is expected to flow. Optionally, the larger the number of the vertical sensing elements that detect the exhale stream, the longer the length of the exhale stream, and the larger the number of the horizontal sensing elements that detect the exhale stream, the wider the exhale stream. Additionally, the amplitude of the temperature changes measured by the sensing elements may also be used to estimate the shape and/or uniformity of the exhale stream. It is noted that when a CAM, from among the at least one CAM, is located above the upper lip and pointed downwards, the vertical sensing elements (from the second example above) also provide data about the width of the exhale stream, and the horizontal sensing elements also provide data about the length of the exhale stream.

In a second example, the at least three regions from which the shape can be inferred are located on (i) at least two vertical positions below the nostrils having a distance above 5 mm between their centers, and (ii) at least two horizontal positions below the nostrils having a distance above 5 mm between their centers. Optionally, the at least three regions represent: (i) parameters of a 3D shape that confines the exhale stream, and TH_(S) are the parameters' values, (ii) locations indicative of different lengths of the exhale stream (such as 8 cm, 16 cm, 24 cm, and 32 cm), and/or (iii) locations indicative of different angles characteristic of directions of some of the different SHAPES of the exhale stream (such as locations indicative of a difference of as at least 5°, 10°, or 25° between the directions of the different SHAPEs).

The potential states corresponding to the different SHAPEs may include various physiological and/or emotional states, and usually have to be learned and classified for each user because they depend on the user's physiological and emotional composition. Additionally, the potential states may include general states corresponding to either being healthy or being unhealthy. In some embodiments, at least some of the potential states may correspond to being in a state in which a certain physiological response is likely to occur in the near future (e.g., within the next thirty minutes). Thus, identifying that the user is in such a state can be used to alert regarding the certain physiological response which the user is expected to have in order for the user and/or some other party to take action to address it.

The feature values generated by the computer in order to calculate the SHAPE may include some of the various feature values described in this disclosure that are used to detect a physiological response. In particular, one or more of the feature values are generated based on TH_(S), and may include raw and/or processed values collected by one or more sensing elements of the at least one CAM. Additionally or alternatively, these feature values may include feature values derived from analysis of TH_(S) in order to determine various characteristics of the user's breathing. The feature values include at least one feature value indicative of the SHAPE. For example, the at least one feature value may describe properties of the thermal patterns of TH_(S). Optionally, the feature values include additional feature values indicative of the breathing rate, breathing rate variability, and/or smoothness of the exhale stream.

The model used to select the user's state based on TH_(S) (and optionally other sources of data) may be, in some embodiments, a machine learning-based model. Optionally, the model is trained based on samples comprising feature values generated based on previous on TH_(S) taken when the user being measured was in a known state. Optionally, the previous TH_(S) include thermal measurements of one or more other users (who are not the user whose state is selected based on TH_(S)); in this case, the model may be considered a general model. Optionally, the previous TH_(S) include thermal measurements of the user whose state is selected based on TH_(S); in this case, the model may be considered personalized for this user. Optionally, the previous TH_(S) include thermal measurements taken during different days. Optionally, for each state from among the potential states, the samples include one or more samples that are generated based on TH_(S) taken while the user being measured was in the state. Optionally, the model was trained based on: previous TH_(S) taken while the user was in a first potential state from among the potential states, and other previous TH_(S) taken while the user was in a second potential state from among the potential states. Optionally, the model was trained based on: previous TH_(S) taken from users while the users were in a first potential state from among the potential states, and other previous TH_(S) taken while the users were in a second potential state from among the potential states. Optionally, for the same breathing rate, respiration volume, and dominant nostril, the computer is configured to select different states when TH_(S) are indicative of different SHAPEs that correspond to different potential states.

For each state from among the potential states, the samples include one or more samples that have a label corresponding to the state. The labels for the samples may be generated based on indications that may come from various sources. In one embodiment, a user whose TH_(S) are used to generate a sample may provide indications about his/her state, such as by entering values via an app when having a headache or an anger attack. Additionally or alternatively, an observer of that user, which may be another person or a software agent, may provide indications about the user's state. For example, a parent may determine that certain behavior patterns of a child correspond to displaying symptomatic behavior of a certain state. In another embodiment, indications of the state of a user whose TH_(S) are used to generate a sample may be determined based on measurements of physiological signals of the user, such as measurements of the heart rate, heart rate variability, galvanic skin response, and/or brain activity (e.g., using EEG).

In some embodiments, characteristics of the user's breathing may be indicative of a future state of the user (e.g., a state to which the user may be transitioning). Thus, certain changes in the characteristics of the user's breathing can be used to predict the future state. In these cases, some samples that include feature values generated based on TH_(S) taken during a certain period may be assigned a label based on an indication corresponding to a future time (e.g., a label corresponding to the state of the user 15 or 30 minutes after the certain period). A model trained on such data may be used to predict the user's state at the future time and/or calculate a value indicative of the probability that the user will be in a certain state a certain amount of time into the future.

Given a set of samples that includes feature values generated based on TH_(S) (and optionally the other sources of data) and labels indicative of the state, the model can be trained using various machine learning-based training algorithms. Optionally, the model may include various types of parameters, depending on the type of training algorithm utilized to generate the model. For example, the model may include parameters of one or more of the following: a regression model, a support vector machine, a neural network, a graphical model, a decision tree, a random forest, and other models of other types of machine learning classification and/or prediction approaches.

In some embodiments, a deep learning algorithm may be used to train the model. In one example, the model may include parameters describing multiple hidden layers of a neural network. In one embodiment, when TH_(S) include measurements of multiple pixels, such as when the at least one CAM includes a FPA, the model may include a convolution neural network (CNN). In one example, a CNN may be utilized to identify certain patterns in the thermal images, such as patterns of temperatures in the region of the exhale stream that may be indicative a respiratory parameter, which involve aspects such as the location, direction, size, and/or shape of an exhale stream from the nose and/or mouth. In another example, determining a state of the user based on one characteristics of the user's breathing (e.g., various respiratory parameters), may be done based on multiple, possibly successive, thermal measurements. Optionally, estimating the state of the user may involve retaining state information about the one or more characteristics that is based on previous measurements. Optionally, the model may include parameters that describe an architecture that supports such a capability. In one example, the model may include parameters of a recurrent neural network (RNN), which is a connectionist model that captures the dynamics of sequences of samples via cycles in the network's nodes. This enables RNNs to retain a state that can represent information from an arbitrarily long context window. In one example, the RNN may be implemented using a long short-term memory (LSTM) architecture. In another example, the RNN may be implemented using a bidirectional recurrent neural network architecture (BRNN).

In order to generate a model suitable for identifying the state of the user in real-world day-to-day situations, in some embodiments, the samples used to train the model are based on thermal measurements (and optionally the other sources of data) taken while the user was in different situations, locations, and/or conducting different activities. For example, the model may be trained based on some sample based on previous thermal measurements taken while the user was indoors and other samples based on other previous thermal measurements taken while the user was outdoors. In another example, the model may be trained based on some sample based on some previous thermal measurements taken while the user was sitting and other samples based on other previous thermal measurements taken while the user was walking.

In one embodiment, the computer detects the SHAPE based on TH_(S). Optionally, the detected SHAPE corresponds to a certain state of the user, and the computer bases the selection of the state on the detected SHAPE. Optionally, the computer generates one or more of the feature values used to select the state based on the detected SHAPE. For example, the one or more feature values may be indicative of various parameters of the SHAPE (e.g., parameters of a 3D geometrical body to which the SHAPE corresponds).

To detect the SHAPE the computer may utilize a model that was trained based on previous TH_(S) of the user. Optionally, the previous TH_(S) of the user were taken during different days. In one embodiment, the model includes one or more reference patterns generated based on the previous TH_(S). Optionally, each reference pattern corresponds to a certain SHAPE, and is based on a subset of the previous TH_(S) for which the certain SHAPE was identified. For example, identifying the certain SHAPE may be done using analysis of thermal images of the exhale stream obtained using an external thermal camera that is not head-mounted and/or by a human expert. In this embodiment, detecting the SHAPE may be done by comparing TH_(S) to the one or more reference thermal patterns and determining whether there is a sufficiently high similarity between the thermal pattern of TH_(S) and at least one of the one or more reference thermal patterns.

In another embodiment, the model may be a machine learning-based model that was trained on samples, with each sample comprising feature values generated based on a subset of the previous TH_(S) (e.g., the subset includes previous TH_(S) taken during a certain period), and a label representing the SHAPE corresponding to the subset of the previous TH_(S). In one example, the feature values include values of temperatures of various sensing elements of the at least one CAM. In another example, the feature values may include low-level image properties obtained by applying various image processing techniques to the subset of the previous TH_(S). In this embodiment, detecting the SHAPE may be done by generating feature values based on TH_(S) and utilizing the model to calculate, based on the feature values, a value indicative of the SHAPE corresponding TH_(S).

The SHAPE is a property that may be independent, at least to a certain extent, of other respiratory parameters. Thus, TH_(S) taken at different times may have different SHAPEs detected, even if some other aspects of the breathing at those times are the same (as determined based on values of certain respiratory parameters). In one example, for the same breathing rate of the user, the computer detects a first SHAPE based on a first TH_(S), and detects a second SHAPE based on a second TH_(S). In this example, the first and second TH_(S) have different thermal patterns, e.g., as determined using a similarity function between vector representations of the first and second TH_(S) (which gives a similarity below a threshold). In another example, for the same breathing rate, respiration volume and dominant nostril, the computer detects a first SHAPE based on a first TH_(S), and detects a second SHAPE based on a second TH_(S) (where the first and second TH_(S) have different thermal patterns).

In one embodiment, the system includes a frame worn on the user's head. Each of the at least one CAM is located less than 15 cm from the user's face and does not occlude any of the user's mouth and nostrils. The at least one CAM includes at least first and second inward-facing head-mounted thermal cameras (CAM1 and CAM2, respectively) that take TH_(ROI1) and TH_(ROI2), respectively. CAM1 is physically coupled to the right half of the frame and captures the exhale stream from the right nostril better than it captures the exhale stream from the left nostril, and CAM2 is physically coupled to the left half of the frame and captures the exhale stream from the left nostril better than it captures the exhale stream from the right nostril. In another embodiment, the at least three regions below the nostrils include a first region on the right side of the user's upper lip, a second region on the left side of the user's upper lip, and a third region on the mouth of the user, where thermal measurements of the third region are indicative of the exhale stream from the user's mouth. In still another embodiment, the at least three regions below the nostrils include a first region comprising a portion of the volume of the air below the right nostril where the exhale stream from the right nostril flows, a second region comprising a portion of the volume of the air below the left nostril where the exhale stream from the left nostril flows, and a third region comprising a portion of a volume protruding out of the mouth where the exhale stream from the user's mouth flows.

In one embodiment, a system configured to present a user's state based on SHAPE, includes a CAM and a UI. The at least one CAM takes thermal measurements of at least three regions below the nostrils (TH_(S)) of the user, where TH_(S) are indicative of SHAPE. The UI present the user's state based on TH_(S). Optionally, for the same breathing rate, the UI presents different states for the user when TH_(S) are indicative of different SHAPEs that correspond to different potential states. Optionally, each of the at least one CAM does not occlude any of the user's mouth and nostrils. Optionally, the system further includes a computer that generates feature values based on TH_(S), and utilizes a model to select the state, from among potential states, based on the feature values.

The following method for selecting a state of a user may be performed by running a computer program having instructions for implementing the method. Optionally, the instructions may be stored on a computer-readable medium, which may optionally be a non-transitory computer-readable medium. In response to execution by a system including a processor and memory, the instructions cause the system to perform the following steps: In Step 1, taking thermal measurements of at least three regions below the nostrils (TH_(S)) of the user utilizing an inward-facing head-mounted thermal camera (CAM); wherein TH_(S) are indicative of SHAPE. In Step 2, generating feature values based on TH_(S), where the feature values are indicative of the SHAPE. And in Step 3, utilizing a model for selecting the state of the user, from among potential states of the user, based on the feature values.

Optionally, the method further includes selecting different states, for the same breathing rate, when TH_(S) are indicative of different SHAPEs that correspond to different potential states. Optionally, the method further includes training the model based on: previous TH_(S) taken while the user was in a first potential state from among the potential states, and other previous TH_(S) taken while the user was in a second potential state from among the potential states.

FIG. 39, FIG. 40, and FIG. 41 illustrate one embodiment of eyeglasses 700 with head-mounted thermal cameras, which are able to differentiate between different states of the user based on thermal patterns of the forehead. The illustrated system includes first and second CAMs (701, 702) mounted to the upper right and left portions of the eyeglasses frame, respectively, to take thermal measurements of the forehead. The system further include a sensor 703 mounted to the bridge, which may be utilized to take measurements (m_(conf)) indicative of an occurrence of one or more of the various confounding factors described herein. The CAMs forward the thermal measurements to a computer that may differentiate, based on the thermal measurements of the forehead, between normal and abnormal states of a user (which are illustrated as normal vs migraine vs angry in FIG. 39, and not angry vs angry in FIG. 40). The computer may further differentiate between extents of a condition, which is illustrated as severe OCD vs less severe OCD after a treatment in FIG. 41.

In one embodiment, a system configured to differentiate between normal and abnormal states, includes at least one CAM and a computer. The at least one CAM is worn on a user's head and takes thermal measurements of at least first and second regions on the right side of the forehead (TH_(R1) and TH_(R2), respectively) of the user. The at least one CAM further takes thermal measurements of at least third and fourth regions on the left side of the forehead (TH_(L1) and TH_(L2), respectively). The middles of the first and third regions are at least 1 cm above the middles of the second and fourth regions, respectively. Each of the least one CAM is located below the first and third regions, and does not occlude any portion of the first and third regions. Optionally, CAM also does not occlude the second and fourth regions. The computer determines, based on TH_(R1), TH_(R2), TH_(L1), and TH_(L2), whether the user is in a normal state or an abnormal state. Preferably, this embodiment assumes that the user's hair does not occlude the first, second, third and fourth regions on the forehead. Optionally, the at least one CAM includes a CAM that includes a sensor and a lens, and the sensor plane is tilted by more than 2° relative to the lens plane according to the Scheimpflug principle in order to capture sharper images by the CAM, when at least one CAM is worn by the user. Here, the lens plane refers to a plane that is perpendicular to the optical axis of the lens, which may include one or more lenses.

In one embodiment, the at least one CAM includes at least first and second inward-facing head-mounted thermal cameras (CAM1 and CAM2, respectively) located to the right and to the left of the vertical symmetry axis that divides the user's face, respectively (i.e., the axis the goes down the center of the user's forehead and nose). CAM1 is configured to take TH_(R1) and TH_(R2), and CAM2 is configured to take TH_(L1) and TH_(L2). Optionally, CAM1 and CAM2 are located at least 1 cm from each other. In one example, CAM1 and CAM2 are 701 and 702 that are illustrated in FIG. 40. Being able to detect a pattern on the forehead may involve utilization of multiple sensing elements (pixels) by each of CAM1 and CAM2. Optionally, each of CAM1 and CAM2 weighs below 10 g, is located less than 10 cm from the user's face, and includes microbolometer or thermopile sensor with at least 6 sensing elements. Optionally, CAM1 includes at least two multi-pixel thermal cameras, one for taking measurements of the first region, and another one for taking measurements of the second region; CAM2 also includes at least two multi-pixel thermal cameras, one for taking measurements of the third region, and another one for taking measurements of the fourth region.

The computer determines, based on TH_(R1), TH_(R2), TH_(L1), and TH_(L2), whether the user is in a normal state or an abnormal state. In one embodiment, the state of the user is determined by comparing TH_(R1), TH_(R2), TH_(L1), and TH_(L2) to reference thermal patterns of the forehead that include at least one reference thermal pattern that corresponds to the normal state and at least one reference thermal pattern that corresponds to the abnormal state. Optionally, a reference thermal pattern is determined from previous TH_(R1), TH_(R2), TH_(L1), and TH_(L2) of the user, taken while the user was in a certain state corresponding to the reference thermal pattern (e.g., normal or abnormal states). Determining whether TH_(R1), TH_(R2), TH_(L1), and TH_(L2), are similar to a reference thermal pattern may be done using various image similarity functions, such as determining the distance between each pixel in the reference thermal pattern and its counterpart in TH_(R1), TH_(R2), TH_(L1), or TH_(L2). One way this can be done is by converting TH_(R1), TH_(R2), TH_(L1), or TH_(L2) into a vector of pixel temperatures, and comparing it to a vector of the reference thermal pattern (using some form of vector similarity metric like a dot product or the L2 norm). Optionally, if the similarity reaches a threshold, the user is considered to be in the state to which the reference thermal pattern corresponds.

In another embodiment, the computer determines that the user is in a certain state (e.g., normal or abnormal) by utilizing a model to calculate, based on feature values generated from TH_(R1), TH_(R2), TH_(L1), and TH_(L2), a value indicative of the extent to which the user is in the certain state. Optionally, the model is trained based on samples, each comprising feature values generated based on previous TH_(R1), TH_(R2), TH_(L1), and TH_(L2) of the user, taken while the user was in the certain state. In some embodiments, determining whether the user is in a certain state involves determining that TH_(R1), TH_(R2), TH_(L1), and TH_(L2) taken during at least a certain period of time (e.g., at least ten seconds, at least one minute, or at least ten minutes) are similar to a reference thermal pattern that corresponds to the certain state.

Being in a normal/abnormal state may correspond to different behavioral and/or physiological responses. In one embodiment, the abnormal state involves the user displaying symptoms of one or more of the following: an anger attack, Attention Deficit Disorder (ADD), and Attention Deficit Hyperactivity Disorder (ADHD). In this embodiment, being in the normal state refers to usual behavior of the user that does not involve displaying said symptoms. In another embodiment, when the user is in the abnormal state, the user will display within a predetermined duration (e.g., shorter than an hour), with a probability above a predetermined threshold, symptoms of one or more of the following: anger, ADD, and ADHD. In this embodiment, when the user is in the normal state, the user will display the symptoms within the predetermined duration with a probability below the predetermined threshold. In yet another embodiment, when the user is in the abnormal state the user suffers from a headache, and when the user is in the normal state, the user does not suffer from a headache. In still another embodiment, the abnormal state refers to times in which the user has a higher level of concentration compared to the normal state that refers to time in which the user has a usual level of concentration. Although the thermal patterns of the forehead are usually specific to the user, they are usually repetitive, and thus the system may able to learn some thermal patterns of the user that correspond to various states.

Touching the forehead can change the forehead's thermal pattern, even though the user's state did not actually change. Optionally, the system further includes a sensor configured to provide an indication indicative of whether the user touches the forehead. Although the touch is expected to influence thermal readings from the touched area, the computer may continue to operate, for a predetermined duration, according to a state identified shortly (e.g., 1-20 sec) before receiving the indication, even if it identifies a different state shortly (e.g., less than 10, 20, 30, or 60 sec) after receiving the indication. In one example, the sensor is a visible-light camera, and the computer uses image processing to determine whether the user touched the forehead and/or for how long.

The computer may alert the user responsive to identifying an irregularity in TH_(R1), TH_(R2), TH_(L1), and TH_(L2), which does not result from interference, such as touching the forehead. For example, the irregularity may involve a previously unobserved thermal pattern of the forehead. Optionally, the user may be questioned in order to determine if there is a medical reason for the irregularity, such as a stroke or dehydration, in which case medical assistance may be offered, e.g., by summoning medical personnel to the user's location. Optionally, the computer alerts the user when identifying that the user is in an abnormal state associated with antisocial behavior (e.g., an anger attack).

Additional thermal cameras may be utilized to take thermal measurements that may be used to detect the user's state. For example, the system may include at least one additional CAM for taking thermal measurements of regions on the nose and below the nostrils (TH_(ROI3) and TH_(ROI4), respectively) of the user. Optionally, the additional CAM weighs below 10 g, is physically coupled to a frame worn on the user's head, and is located less than 15 cm from the face. Optionally, the computer determines the user's state also based on TH_(ROI3) and TH_(ROI4). Optionally, the computer (i) generates feature values based on TH_(R1), TH_(R2), TH_(L1), TH_(L2), TH_(ROI3), and TH_(ROI4), and (ii) utilizes a model to determine the user's state based on the feature values. Optionally, the model was trained based on a first set of previous TH_(R1), TH_(R2), TH_(L1), TH_(L2), TH_(ROI3), and TH_(ROI4) taken while the user was in the normal state and a second set of previous TH_(R1), TH_(R2), TH_(L1), TH_(L2), TH_(ROI3), and TH_(ROI4) taken while the user was in the abnormal state.

In another example, the system may include another CAM for taking thermal measurements of a region on the periorbital area (TH_(ROI3)) of the user. Optionally, the computer determines the state of the user also based on TH_(ROI3). Optionally, the computer is further configured to: (i) generate feature values based on TH_(R1), TH_(R2), TH_(L1), TH_(L2), and TH_(ROI3), and (ii) utilize a model to determine the user's state based on the feature values. Optionally, the model was trained based on a first set of previous TH_(R1), TH_(R2), TH_(L1), TH_(L2), and TH_(ROI3) taken while the user was in the normal state and a second set of previous TH_(R1), TH_(R2), TH_(L1), TH_(L2), and TH_(ROI3) taken while the user was in the abnormal state.

Determining the user's state based on TH_(R1), TH_(R2), TH_(L1), and TH_(L2) (and optionally other sources of data) may be done using a machine learning-based model. Optionally, the model is trained based on samples comprising feature values generated based on previous TH_(R1), TH_(R2), TH_(L1), and TH_(L2) taken when the user was in a known state (e.g., for different times it was known whether the user was in the normal or abnormal state). Optionally, the user may provide indications about his/her state, such as by entering values via an app when having a headache or an anger attack. Additionally or alternatively, an observer of the user, which may be another person or a software agent, may provide the indications about the user's state. For example, a parent may determine that certain behavior patterns of a child correspond to displaying symptomatic behavior of ADHD. In another example, indications of the state of the user may be determined based on measurements of physiological signals of the user, such as measurements of the heart rate, heart rate variability, breathing rate, galvanic skin response, and/or brain activity (e.g., using EEG).

In some embodiments, one or more of the feature values in the samples may be based on other sources of data (different from TH_(R1), TH_(R2), TH_(L1), and TH_(L2)). These may include additional thermal cameras, additional physiological measurements of the user, and/or measurements of the environment in which the user was while the measurements were taken. In one example, at least some of the feature values used in samples include additional physiological measurements indicative of one or more of the following signals of the user: heart rate, heart rate variability, brainwave activity, galvanic skin response, muscle activity, and extent of movement. In another example, at least some of the feature values used in samples include measurements of the environment that are indicative of one or more of the following values of the environment in which the user was in: temperature, humidity level, noise level, air quality, wind speed, and infrared radiation level.

Given a set of samples comprising feature values generated based on TH_(R1), TH_(R2), TH_(L1), and TH_(L2) (and optionally the other sources of data) and labels generated based on the indications, the model can be trained using various machine learning-based training algorithms. Optionally, the model is utilized by a classifier that classifies the user's state (e.g., normal/abnormal) based on feature values generated based on TH_(R1), TH_(R2), TH_(L1), and TH_(L2) (and optionally the other sources). Optionally, the model may include various types of parameters, depending on the type of training algorithm utilized to generate the model. For example, the model may include parameters of one or more of the following: a regression model, a support vector machine, a neural network, a graphical model, a decision tree, a random forest, and other models of other types of machine learning classification and/or prediction approaches.

In some embodiments, the model is trained utilizing deep learning algorithms. Optionally, the model includes parameters describing multiple hidden layers of a neural network. Optionally, the model includes a convolution neural network (CNN), which is useful for identifying certain patterns in the thermal images, such as patterns of temperatures on the forehead. Optionally, the model may be utilized to identify a progression of a state of the user (e.g., a gradual forming of a certain thermal pattern on the forehead). In such cases, the model may include parameters that describe an architecture that supports a capability of retaining state information. In one example, the model may include parameters of a recurrent neural network (RNN), which is a connectionist model that captures the dynamics of sequences of samples via cycles in the network's nodes. This enables RNNs to retain a state that can represent information from an arbitrarily long context window. In one example, the RNN may be implemented using a long short-term memory (LSTM) architecture. In another example, the RNN may be implemented using a bidirectional recurrent neural network architecture (BRNN).

In order to generate a model suitable for identifying the state of the user in real-world day-to-day situations, in some embodiments, the samples used to train the model are based on thermal measurements (and optionally the other sources of data) taken while the user was in different situations, locations, and/or conducting different activities. In a first example, the model may be trained based on a first set of previous thermal measurements taken while the user was indoors and in the normal state, a second set of previous thermal measurements taken while the user was indoors and in the abnormal state, a third set of previous thermal measurements taken while the user was outdoors and in the normal state, and a fourth set of previous thermal measurements taken while the user was outdoors and in the abnormal state. In a second example, the model may be trained based on a first set of previous thermal measurements taken while the user was sitting and in the normal state, a second set of previous thermal measurements taken while the user was sitting and in the abnormal state, a third set of previous thermal measurements taken while the user was standing and/or moving around and in the normal state, and a fourth set of previous thermal measurements taken while the user was standing and/or moving around and in the abnormal state. Usually the movements while standing and/or moving around, and especially when walking or running, are greater compared to the movement while sitting; therefore, a model trained on samples taken during both sitting and standing and/or moving around is expected to perform better compared to a model trained on samples taken only while sitting.

Having the ability to determine the state of the user can be advantageous when it comes to scheduling tasks for the user and/or making recommendations for the user, which suits the user's state. In one embodiment, responsive to determining that the user is in the normal state, the computer prioritizes a first activity over a second activity, and responsive to determining that the user is in the abnormal state, the computer prioritizes the second activity over the first activity. Optionally, accomplishing each of the first and second activities requires at least a minute of the user's attention, and the second activity is more suitable for the abnormal state than the first activity. Optionally, and the first activity is more suitable for the normal state than the second activity. Optionally, prioritizing the first and second activities is performed by a calendar management program, a project management program, and/or a “to do” list program. Optionally, prioritizing a certain activity over another means one or more of the following: suggesting the certain activity before suggesting the other activity, suggesting the certain activity more frequently than the other activity (in the context of the specific state), allotting more time for the certain activity than for the other activity, and giving a more prominent reminder for the certain activity than for the other activity (e.g., an auditory indication vs. a mention in a calendar program that is visible only if the calendar program is opened).

Such state-dependent prioritization may be implemented in various scenarios. In one example, the normal state refers to a normal concentration level, the abnormal state refers to a lower than normal concentration level, and the first activity requires a high attention level from the user compared to the second activity. For instance, the first and second activities may relate to different topics of a self-learning program for school; when identifying that the user is in the normal concentration state, a math class is prioritized higher than a sports lesson; and when identifying that the user is in the lower concentration state, the math class is prioritized lower than the sports lesson. In another example, the normal state refers to a normal anger level, the abnormal state refers to a higher than normal anger level, and the first activity involves more interactions of the user with other humans compared to the second activity. In still another example, the normal state refers to a normal fear level, the abnormal state refers to a panic attack, and the second activity is expected to have a more relaxing effect on the user compared to the first activity.

In one embodiment, a system configured to alert about an abnormal state includes at least one CAM and a user interface (UI). The at least one CAM takes thermal measurements of at least first and second regions on the right side of the forehead (TH_(R1) and TH_(R2), respectively) of the user, and takes thermal measurements of at least third and fourth regions on the left side of the forehead (TH_(L1) and TH_(L2), respectively). The middles of the first and third regions are at least 1 cm above the middles of the second and fourth regions, respectively. Each of the at least one CAM is located below the first and third regions, and does not occlude any portion of the first and third regions. The UI provides an alert about an abnormal state of the user, where the abnormal state is determined based on TH_(R1), TH_(R2), TH_(L1), and TH_(L2). Optionally, the system includes a transmitter that may be used to transmit TH_(R1), TH_(R2), TH_(L1), and TH_(L2) to a computer that determines, based on TH_(R1), TH_(R2), TH_(L1), and TH_(L2), whether the user is in the normal state or the abnormal state. The computer may include a wearable computer, a computer belonging to a smartphone or a smartwatch carried by the user, and/or cloud-based server. Optionally, responsive to determining that the user is in an abnormal state, the computer commands the UI to provide the alert. For example, the computer may send a signal to a smartphone app, and/or to a software agent that has control of the UI, to provide the alert. In another example, the computer may send an instruction to the UI to provide the alert. Optionally, the alert is provided as text, image, sound, and/or haptic feedback.

The following method for alerting about an abnormal state may be used, in some embodiments, by the system configured to alert about the abnormal state (described above). The steps described below may be performed by running a computer program having instructions for implementing the method. Optionally, the instructions may be stored on a computer-readable medium, which may optionally be a non-transitory computer-readable medium. In response to execution by a system including a processor and memory, the instructions cause the system to perform the following steps:

In Step 1, taking thermal measurements of at least first and second regions on the right side of the forehead (TH_(R1), TH_(R2)) of a user, and thermal measurements of at least third and fourth regions on the left side of the forehead (TH_(L1), TH_(L2)) of the user. The middles of the first and third regions are at least 1 cm above the middles of the second and fourth regions, respectively.

In Step 2, generating feature values based on TH_(R1), TH_(R2), TH_(L1), and TH_(L2).

In Step 3, utilizing a model for detecting a state of the user based on the feature values. The model was trained based on (i) previous feature values taken while the user was in a normal state, and (ii) other previous feature values taken while the user was in the abnormal state.

And in Step 4, responsive to detecting the abnormal state in Step 3, alerting about the abnormal state. In one example, the alerting may involve providing text, image, sound, and/or haptic feedback via the user interface.

Neurofeedback sessions can assist in treating various brain function-related conditions and/or disorders. In order to maximize their effectives, it may be advantageous to have neurofeedback treatments while a person suffers and/or exhibits the symptoms of a brain function-related condition and/or disorder. The following are descriptions of embodiments of a wearable system that may be utilized for this purpose. Some embodiments of a neurofeedback system described below involve a wearable, lightweight device that is aesthetically acceptable, and may be utilized as needed in day-to-day situations.

Some examples of disorders that may be treated with some embodiments of the neurofeedback system described herein include disorders related to (i) frontal lobe dysfunction, such as ADHD, headaches, anger, anxiety, and depression, (ii) paroxysmal disorders, such as headaches, seizures, rage reactions, and panic attacks, (iii) chronic pain, and (iv) stress. It is noted that the term “neurofeedback” also covers biofeedback and other similar feedback-based treatments.

FIG. 38 (already discussed above) illustrates one embodiment of a system configured to provide neurofeedback (based on measurements of CAM 720) and/or breathing biofeedback (based on measurements of at least some of thermal cameras 723, 725, 727 and 729). The system illustrated in FIG. 41, which uses two inward-facing head-mounted thermal cameras (701 and 702) to measure the forehead, may be used for neurofeedback together with a UI (not illustrated). Other embodiments of neurofeedback HMSs may involve more than two inward-facing head-mounted thermal cameras to measure the forehead. Some embodiments of neurofeedback HMSs may include one or more sensors such as the sensor 722, which are used to take m_(conf) as discussed below.

FIG. 43 illustrates a scenario in which a user has neurofeedback session during a day-to-day activity, such as during school time. For example, the session may be initiated because the user felt that he was losing concentration and/or the system might have determined that the user was exhibiting symptoms of ADHD and/or was in an undesirable state. The user wears an Augmented Reality device (AR), which includes user interface 710 that includes a display to present the augmented images. The AR includes one or more inward-facing head-mounted thermal cameras, which may be similar to the system illustrated in FIG. 38. The neurofeedback session involves attempting to control brain activity by causing the augmented reality video of the car 711 to drive forwards. For example, the car 711 drives forwards when the temperature at certain regions of the forehead 712 increases, and drives backwards when the temperature at the certain regions of the forehead 712 decreases.

In one embodiment, a neurofeedback system includes at least an inward-facing head-mounted thermal camera (CAM) and a user interface (UI). Optionally, the neurofeedback system may include additional elements such as a frame, a computer, and/or additional sensors and/or thermal cameras, as described below.

CAM is worn on a user's head and takes thermal measurements of a region on the forehead (TH_(F)) of the user. CAM is positioned such that when the user is upright, CAM is located below the middle of the region on the user's forehead. Optionally, CAM does not occlude the center of the forehead, and as such, may be more aesthetically pleasing than systems that have elements that occlude the center of the forehead. Optionally, CAM is located close to the forehead, at a distance below 15 cm, 10 cm, or 5 cm from the user's face. Optionally, CAM may use a single pixel sensor (e.g., discrete thermophile sensor) or a multiple pixel sensor (e.g., microbolometer FPA).

In one embodiment, TH_(F) measured by CAM includes the area known in the field of electroencephalography as the “Fpz point”, which is typically located at a point that is between 5% and 15% the distance from the nasion to the Inion (e.g., approximately at around 10% the distance). Optionally, in this embodiment, TH_(F) may be indicative of temperature changes at the Fpz point. Additionally or alternatively, the region on the forehead measured by CAM may include the center of the forehead, and TH_(F) may optionally be indicative of temperature changes at the center of the forehead.

In another embodiment, CAM may measure at least four areas on the user's forehead covering regions on the upper right side of the forehead, lower right side of the forehead, upper left side of the forehead, and lower left side of the forehead, respectively. Optionally, in this embodiment, TH_(F) may be indicative of a thermal pattern of the user's forehead. Optionally, in this embodiment, “CAM” refers to multiple inward-facing thermal cameras, which include at least first and second inward-facing head-mounted thermal cameras (CAM1 and CAM2, respectively). CAM1 takes the measurements of the upper right side of the forehead and the lower right side of the forehead, and CAM2 takes the measurements of the upper left side of the forehead and the lower left side of the forehead. Optionally, TH_(F) may include measurements of at least six areas on the user's forehead. Optionally, the at least four areas and the at least six areas each include at least one area that covers the Fpz point.

Due to the proximity of CAM to the face, in some embodiments, there may be an acute angle between the optical axis of CAM and the forehead. In order to improve the sharpness of thermal images of the forehead, in some embodiments, CAM may include a sensor and a lens, which are configured such that the sensor plane is tilted by more than 2° relative to the lens plane according to the Scheimpflug principle, which may enable the capture of sharper images of the forehead when CAM is close to the face.

The UI provides a feedback to the user during the neurofeedback session, which is determined based on TH_(F) and optionally m_(conf) (that is indicative of confounding factors). Optionally, providing the session for the user involves receiving instructions from the user (e.g., verbal commands and/or menu selections), which may affect the type of feedback the user receives (e.g., what type of session or “game” will be played in the session, how long the session should last, etc.).

In some embodiments, at least some of the feedback presented to the user via the UI is intended to indicate to the user whether, and optionally to what extent, the user's brain activity (as determined based on TH_(F)) is progressing towards a target. Optionally, the target may correspond to a state of brain activity that causes TH_(F) to have a certain value. Optionally, the target may correspond to a typical TH_(F) pattern of the user. Optionally, typical TH_(F) pattern of the user is a pattern of temperatures on different points on the forehead, which determined based on previous TH_(F) that are measured when the user was in a typical, normal state, and not exhibiting symptoms of anger, ADHD, a headache, etc. In one example, the user may be considered to make progress in the neurofeedback session if the temperature of the forehead (or a certain region on the forehead) becomes closer to a target temperature. In another example, the user may be considered to make progress in the neurofeedback session if the variability of temperatures across certain regions of the forehead reduces. In yet another example, the user may be considered to make progress in the neurofeedback session if asymmetry of temperatures of the forehead reduces. And in still another example, the user may be considered to make progress in the neurofeedback session if TH_(F) pattern measured during the session becomes more similar to a certain target thermal pattern. Optionally, the user may receive feedback indicative of decreasing positive progress (or negative progress) when the TH_(F) pattern measured during the session becomes less similar to the typical TH_(F) pattern.

In one embodiment, video played as part of the feedback is played according to a protocol suitable for a passive infrared hemoencephalography (pIR HEG) session, which is a form of biofeedback for the brain that measures and displays information on the thermal output of the frontal lobe. In one configuration, pIR HEG involves increasing the forehead temperature by watching a movie that provides the feedback. The movie plays when the measured forehead temperature rises and stops when the temperature drops. The system may increase the threshold as the user learns how to raise the forehead temperature, and the user is instructed to calmly concentrate on making the movie continue to play.

The computer controls the neurofeedback session based on TH_(F) and optionally m_(coif). In one embodiment, the computer compares TH_(F) to a target temperature. Optionally, different pixels of CAM may be compared to different target temperatures, or the target temperature may refer to an average temperature of the forehead. In another embodiment, the computer may calculate changes to temperature of the forehead (ΔT_(F)) based on TH_(F), and utilizes ΔT_(F) to control the neurofeedback session. In yet another embodiment, the computer may compare TH_(F) to a target thermal pattern of the forehead, and the progress of the user in the neurofeedback session is evaluated based on a similarity between TH_(F) and the target thermal pattern, and/or a change in extent of similarity between TH_(F) and the target thermal pattern.

In one embodiment, TH_(F) includes measurements of at least four non-collinear regions on the forehead (e.g., all the four regions do not lie on the same straight line), and the computer controls the neurofeedback session by providing the user a feedback via the user interface. The computer calculates a value indicative of similarity between a current TH_(F) pattern and a previous TH_(F) pattern of the user taken while the user was in a target state, and generates, based on the similarity, the feedback provided to the user as part of the neurofeedback session. The TH_(F) pattern may refer to a spatial pattern of the at least four non-collinear regions on the forehead (e.g., a pattern in a thermal image received from a FPA sensor), and/or to a pattern in the time domain of the at least four non-collinear regions on the forehead (e.g., a pattern detected in a time series of the thermal measurements).

Neurofeedback sessions may have different target states in different embodiments. Generally, the purpose of a session is to bring the user's state during the neurofeedback session (the “present state”) to become more similar to a target state. In one embodiment, while the user was in the target state, one or more of the following were true: the user was healthier compared to the present state, the user was more relaxed compared to the present state, a stress level of the user was below a threshold, the user's pain level was below a threshold, the user had no headache, the user did not suffer from depression, and the user was more concentrated compared to the present state. Additionally, the computer may receive an indication of a period during which the user was in the target state based on a report made by the user (the previous TH_(F) pattern comprises TH_(F) taken during the period), measurements of the user with a sensor other than CAM, semantic analysis of text written by the user, and/or analysis of the user's speech.

In some embodiments, the computer may utilize a machine learning-based model to determine whether the session is successful (or is expected to be) and/or to determine the user's progress in the neurofeedback session at a given time. Optionally, the computer generates feature values based on TH_(F), and utilizes the model to calculate a value indicative of the progress and/or session success. Optionally, the model is trained on samples comprising feature values based on previously taken TH_(F) and labels indicative of the success of the session and/or progress at the time those TH_(F) were taken. Optionally, the samples may be generated based on previously taken TH_(F) of the user and/or of other users. Optionally, the samples include samples generated based on TH_(F) of the user taken on different days, and/or while the user was in different situations.

At a given time, temperatures measured at different areas of the forehead may be different. A value, which is a function of the temperatures at the different areas and is indicative of their variability, may be referred to herein as the “temperature variability” of the measurements. In one example, the function of the temperatures is the statistical variance of the temperatures. Having high temperature variability can be a sign that the user is suffering from various conditions, such as anger, a headache, depression, and/or anxiety. Optionally, a target of the neurofeedback session may be to lower the temperature variability of TH_(F). Optionally, progress of the neurofeedback session may be evaluated based on a value of the temperature variability of TH_(F), an extent that the temperature variability of TH_(F) has decreased, and/or a rate at which the temperature variability of TH_(F) has decreased.

Various brain function-related conditions may be manifested via asymmetrical thermal patterns on the forehead. Optionally, a target of a neurofeedback session in such cases may be to decrease the asymmetry of the thermal patterns. In one embodiment, CAM is located to the right of the vertical symmetry axis that divides the user's face (e.g. 701), and the region is on the right side of the forehead. The neurofeedback system may include a second inward-facing head-mounted thermal camera (e.g. 702), located to the left of the vertical symmetry axis, which takes thermal measurements of a second region on the left side of the forehead (TH_(F2)). Optionally, the computer provides to the user a feedback that becomes more positive as the temperature asymmetry between TH_(F) and TH_(F2) decreases.

Different regions on the forehead may be associated with different importance, with respect to various physiological responses and/or conditions that may be treated with neurofeedback sessions. In one embodiment, regions that are more important are associated with higher weights compared to weights associated with regions that are less important. Optionally, these weights may be utilized by the computer to calculate various values such as an average temperature of the forehead, which with the weights may be considered a “weighted average temperature”. Similarly, a temperature variability of TH_(F) that is calculated while taking into account the weights associated with the various areas may be a “weighted temperature variability”, and temperature asymmetry between TH_(F) and TH_(F2), which is calculated while taking into account the weights associated with the various areas may be a “weighted temperature asymmetry”. In some embodiments, providing feedback to the user based on one or more of the above “weighted” values may increase the efficacy of the neurofeedback session.

The temperature variability may be an indicator for the success or failure of the neurofeedback session. A session that causes a decreasing of the temperature variability below a certain first threshold may be considered a successful session that can be terminated, while a session that causes an increase of the temperature variability above a certain second threshold may be considered a failed session that should be terminated in order to prevent worsening the symptoms. In one embodiment, the computer terminates the neurofeedback session when TH_(F) are indicative of the temperature variability decreasing below the certain first threshold. Additionally or alternatively, the computer may terminate the neurofeedback session when TH_(F) are indicative of the temperature variability increasing above the certain second threshold.

In a similar fashion, the temperature asymmetry may be an indicator for the success or failure of the neurofeedback session for certain disorders. In one embodiment, the computer terminates the neurofeedback session when TH_(F) are indicative of the temperature asymmetry decreasing below a certain first threshold. Additionally or alternatively, the computer may terminate the neurofeedback session when TH_(F) are indicative of the temperature asymmetry increasing above a certain second threshold.

Having neurofeedback sessions, in a real world, day-to-day situations can involve conditions that are less sterile and not as controlled as the conditions that typically encountered when conducting such sessions at a clinic or a laboratory. In particular, thermal measurements of the forehead may be affected by various factors that are unrelated to the type of brain activity the user is conducting, as part of the session; these factors may often be absent and/or less extreme in controlled settings and/or may be noticed and accounted for by a practitioner (who for example, may tell the user not to touch the forehead). Such factors may be referred to herein as confounding factors. Some examples of confounding factors include touching the forehead (e.g., with one's fingers), thermal radiation directed at the forehead (e.g., direct sunlight), and direct airflow on the forehead (e.g., from an air conditioner). Each of these factors can cause changes in TH_(F) that are not due to brain activity. In order to account for one or more of these confounding factors, in some embodiments, the neurofeedback includes a wearable sensor that takes measurements (denoted m_(conf)) indicative of at least one of the following confounding factors: touching the forehead, thermal radiation directed at the forehead, and direct airflow on the forehead. Optionally, the wearable sensor is coupled to a frame worn on the user's head. The following are some examples of types of sensors that the wearable sensor may involve in some embodiments of the neurofeedback system.

In one embodiment, the wearable sensor is an outward-facing head-mounted thermal camera (CAM_(out)) that takes thermal measurements of the environment (THEN). Optionally, the angle between the optical axes of CAM and CAM_(out) is at least one or more of the following angles: 45°, 90°, 130°, 170°, and 180°. In another embodiment, the wearable sensor provides measurements indicative of times at which the user touches the forehead. Optionally, the wearable sensor includes a visible-light camera, a miniature radar (such as low-power radar operating in the range between 30 GHz and 3,000 GHz), an active electro-optics distance measurement device (such as a miniature Lidar), and/or an ultrasound sensor. In yet another embodiment, the sensor may be an anemometer that is physically coupled to a frame worn on the user's head, is located less than 15 cm from the face, and provides a value indicative of a speed of air directed at the face.

There are various way in which the computer may utilize m_(conf) to account for occurrences of a confounding factor during the neurofeedback session. In one embodiment, an occurrence of the confounding factor may prompt the computer to alert the user about the occurrence. In one example, the computer may identify, based on m_(conf), that the extent of a confounding factor reached a threshold, and command the user interface to alert the user that the neurofeedback session is less accurate due to the confounding factor. In another example, upon identifying that the extent of a confounding factor reached the threshold, the computer may refrain from updating the feedback provided to the user as part of the neurofeedback session for at least a certain duration. The certain duration may be a fixed period (e.g., 0.2 seconds from reaching the threshold), and/or may last until m_(conf) indicate that the extent of the confounding factor is below the threshold.

In one embodiment, the computer may adjust the values of TH_(F) based on the values of m_(conf) according to a certain function and/or transformation. For example, TH_(F) may be normalized with respect to the intensity of thermal radiation directed at the face and/or the speed of wind directed at the face. In another embodiment, in which the computer utilizes the machine learning-based model to calculate a value indicative of the progress and/or success of the session, the computer may utilize m_(conf) to generate at least some of the feature values that are utilized to calculate the value indicative of the progress and/or success. Optionally, the model is trained based on samples that include at least some samples that are based on TH_(F) and m_(conf) that were taken while a confounding factor affected TH_(F).

Another approach that may be utilized by the computer, in some embodiments, is to learn to differentiate between changes to TH_(F) due to brain activity and changes to TH_(F) due to various confounding factors (which may have different characteristics). In one embodiment, the computer may generate feature values based on sets of TH_(F) and m_(conf), and utilize a second machine learning-based model to detect, based on the feature values, whether a change in TH_(F) occurred responsive to brain activity or a confounding factor. Optionally, the second model may be trained on samples generated based on measurements taken at times that a confounding factor affected TH_(F) and on other samples based on measurements taken at times that the confounding factor did not affect TH_(F).

It is to be noted that since in real-world scenarios confounding factors can affect TH_(F), utilizing one or more of the various measures described above may assist the computer to provide better neurofeedback sessions. Thus, in some embodiments, on average, neurofeedback sessions based on TH_(F) and m_(conf) provide better results than neurofeedback sessions based on TH_(F) without m_(conf).

In addition to confounding factors of which m_(conf) may be indicative, in some embodiments, the computer may take into account in a similar way, other cofounding factors. In one embodiment, the neurofeedback system may include an additional wearable and/or head-mounted sensor used to detect a movement of the frame relative to the head while the frame is still worn, a change in the user's position, and/or a change in the user's body temperature. In another embodiment, the neurofeedback system may include a humidity sensor and/or an environmental temperature sensor, which may be coupled to the user.

Consumption of various substances may also be considered confounding factors. In one embodiment, the computer may receive an indication of whether the user took medication before the neurofeedback session (e.g., the type of medication and dosage), whether the user smoked, consumed alcohol, etc. Each of these factors may affect TH_(F) in certain ways that may not necessarily be because of the user's brain activity. In a similar way to how the computer handles confounding factors in the description above, the computer may warn about the session being ineffective (e.g., after consuming alcohol or drugs) and/or perform various normalizations and/or computations to address these confounding factors (e.g., by generating feature values indicating the consumption of the substances).

Another way in which some confounding factors may be addressed, involves providing better insolation for the forehead region from the environment while the neurofeedback session is being conducted. To this end, one embodiment involves utilization of a clip-on structure designed to be attached and detached from the frame multiple times (e.g., it may be attached before a neurofeedback session starts and detached after the session terminates). Optionally, the clip-on includes a cover that occludes (when attached to the frame) the forehead region measured by CAM, which drives the neurofeedback. The clip-on may protect the region against environmental radiation, wind, and touching the region. FIG. 42 illustrates a clip-on 716 configured to be attached and detached from the frame 700 multiple times. The clip-on 716 includes a cover configured to occlude the region on the user's forehead (when the clip-on is attached to the frame) and a mechanism that holds the clip-on to the frame.

This selective use of the clip-on 716 can enable CAM 718 to provide different types of measurements. For example, TH_(F) taken while the clip-on is attached may be less noisy then measurements taken when the clip-on is not attached. In some embodiments, measurements obtained without the clip-on may be too noisy for an effective neurofeedback session due to environmental confounding factors. Thus, in one embodiment, CAM may be used to detect that the user needs a neurofeedback session while the clip-on does not cover the region on the forehead (e.g., based on a thermal pattern of the forehead that indicates that the user is in an abnormal state). Optionally, the user is prompted to attach the clip-on and commence with the neurofeedback session. After the clip-on is attached, CAM takes TH_(F) that are used effectively for the neurofeedback session (and may be of better quality than TH_(F) taken when the clip-on is not attached).

The neurofeedback system may include, in some embodiments, one or more additional CAMs to measure physiological signals indicative of respiration, stress, and other relevant parameters. Optionally, a target of the neurofeedback session may include bringing these physiological signals to a certain value in addition to a target that is related to TH_(F).

In one example, the neurofeedback system may include a second inward-facing head-mounted thermal camera (CAM2) that takes thermal measurements of a region below the nostrils (TH_(N)), which is indicative of the user's breathing. Optionally, the computer may control the neurofeedback session also based on TH_(N). Optionally, TH_(N) is utilized to calculate values of one or more respiratory parameters, such as breathing rate, exhale duration, and/or smoothness of the exhale stream. Optionally, a target state for the neurofeedback session involves having certain values of the one or more respiratory parameters fall in certain ranges. In one example, CAM2 may be the thermal camera 727 or the thermal camera 729, which are illustrated in FIG. 38. Optionally, the computer calculates the user's breathing rate based on TH_(N), and guides the user to breathe at his/her resonant frequency, which maximizes the amplitude of respiratory sinus arrhythmia and is in the range of 4.5 to 7.0 breaths/min.

In another example, the neurofeedback system may include second and third inward-facing head-mounted thermal cameras (CAM2 and CAM3, respectively), which take thermal measurements of regions on the periorbital area and the nose (TH_(ROI2) and TH_(ROI3), respectively). Optionally, the computer may control the neurofeedback session also based on TH_(ROI2) and TH_(ROI3). For example, the computer may calculate a stress level of the user based on TH_(ROI2) and/or TH_(ROI3), and a target state of the neurofeedback session may correspond to a certain stress level the user is supposed to have. Optionally, TH_(ROI2) and TH_(ROI3) may be utilized to calculate a stress level of the user. For example, CAM2 may be the thermal camera 724 or 726, and CAM3 may be the thermal camera 733, which are illustrated in FIG. 38.

The following method for conducting a neurofeedback session may be used, in some embodiments, by systems modeled according to FIG. 38. The steps described below may be performed by running a computer program having instructions for implementing the method. Optionally, the instructions may be stored on a computer-readable medium, which may optionally be a non-transitory computer-readable medium. In response to execution by a system including a processor and memory, the instructions cause the system to perform the following steps:

In Step 1, taking thermal measurements of a region on a forehead (TH_(F)) of the user, from a location below the middle of the region on the user's forehead and less than 10 cm from the user's forehead.

In Step 2, taking measurements (m_(conf)) indicative of at least one of the following confounding factors: touching the forehead, thermal radiation directed at the forehead, and direct airflow on the forehead.

And in Step 3, conducting a neurofeedback session for the user based on TH_(F) and m_(conf). Optionally, the neurofeedback session is controlled by a computer, as described above. Optionally, the method further includes generating feature values based on TH_(F) and m_(conf), and utilizing a model to control the neurofeedback session based on the feature values. Optionally, the model was trained on samples generated based on (i) previous TH_(F) and m_(conf) of the user, and/or (ii) previous TH_(F) and m_(conf) of other users.

Various physiological responses may be detected based on thermal measurements and images of various regions of the face. In one embodiment, a system configured to detect a physiological response includes an inward-facing head-mounted thermal camera (CAM), an inward-facing head-mounted visible-light camera (VCAM), and a computer. The system may optionally include additional elements such as a frame and additional cameras.

CAM is worn on a user's head and takes thermal measurements of a first ROI (TH_(ROI1)) on the user's face. Optionally, CAM weighs below 10 g. Optionally, CAM is located less than 15 cm from the user's face. Optionally, CAM utilizes a microbolometer or a thermopile sensor. In one embodiment, CAM includes a focal-plane array (FPA) sensor and an infrared lens, and the FPA plane is tilted by more than 2° relative to the infrared lens plane according to the Scheimpflug principle in order to improve the sharpness of the image of ROI₁ (where the lens plane refers to a plane that is perpendicular to the optical axis of the lens, which may include one or more lenses).

VCAM is worn on the user's head and takes images of a second ROI (IM_(ROI2)) on the user's face. Optionally, VCAM weighs below 10 g and is located less than 15 cm from the face. Optionally, ROI₁ and ROI₂ overlap (which means extend over so as to cover at least partly). For example, ROI₂ may cover at least half of the area covered by ROI₁. In one embodiment, VCAM includes a multi-pixel sensor and a lens, and the sensor plane is tilted by more than 2° relative to the lens plane according to the Scheimpflug principle in order to improve the sharpness of the image of ROI₂.

It is to be noted that in some embodiments the system may be constructed in a way that none of the system's components (including the frame and cameras) occludes ROI₁ and/or ROI₂. In alternative embodiments, the system may be constructed in a way that at least some of the system components (e.g., the frame and/or CAM) may occlude ROI₁ and/or ROI₂.

The computer detects the physiological response based on TH_(ROI1), IM_(ROI2), and a model. Optionally, the model includes one or more thresholds to which TH_(ROI1) and/or IM_(ROI2) may be compared in order to detect the physiological response. Optionally, the model includes one or more reference time series to which TH_(ROI1) and/or IM_(ROI2) may be compared in order to detect the physiological response. Optionally, the computer detects the physiological response by generating feature values based on TH_(ROI1) and IM_(ROI2), and utilizing the model to calculate, based on the feature values, a value indicative of the extent of the physiological response. In this case, the model may be referred to as a “machine learning-based model”. Optionally, at least some of the feature values, which are generated based on IM_(ROI2) may be used to identify, and/or account for, various confounding factors that can alter TH_(ROI1) without being directly related to the physiological response. Thus, on average, detections of the physiological responses based on TH_(ROI1) and IM_(ROI2) are more accurate than detections of the physiological responses based on TH_(ROI1) without IM_(ROI2).

In one example, the physiological response is indicative of an occurrence of at least one of the following emotional states of the user: joy, fear, sadness, and anger. In another example, the physiological response is indicative of an occurrence of one or more of the following: stress, mental workload, an allergic reaction, a headache, dehydration, intoxication, and a stroke. The physiological response may be a physiological signal of the user. In one example, the physiological response is a heart rate of the user, and in this example, ROI₁ is on the skin above at least one of the superficial temporal artery and the frontal superficial temporal artery. In another example, the physiological response is frontal lobe brain activity of the user, and in this example, ROI₁ is on the forehead. In still another example, the physiological signal is a breathing rate of the user, and ROI₁ is on the nasal area.

A machine learning-based model used to detect a physiological response is typically trained on samples, where each sample includes feature values generated based on TH_(ROI1) and IM_(ROI2) taken during a certain period, and a label indicative of the physiological response of the user during the certain period. Optionally, the model is trained on samples generated based on measurements of the user (in which case the model may be considered a personalized model of the user). Optionally, the model is trained on samples generated based on measurements of one or more other users. Optionally, the samples are generated based on measurements taken while the user being measured was in different situations. Optionally, the samples are generated based on measurements taken on different days.

In some embodiments, images such as IM_(ROI2) may be utilized to generate various types of feature values, which may be utilized to detect the physiological response and/or detect an occurrence of a confounding factor. Some of the feature values generated based on images may include high-level facial-related feature values and their derivatives, such as location and dimensions of facial features and/or landmarks, identification of action units (AUs) in sequences of images, and/or blendshape weights. Other examples of features include various low-level features such as features generated using Gabor filters, local binary patterns (LBP) and their derivatives, algorithms such as SIFT and/or SURF (and their derivatives), image keypoints, histograms of oriented gradients (HOG) descriptors, and statistical procedures such independent component analysis (ICA), principal component analysis (PCA), or linear discriminant analysis (LDA). Yet other examples of feature values may include features derived from multiple images taken at different times, such as volume local binary patterns (VLBP), cuboids, and/or optical strain-based features. Additionally, some of the feature values may be based on other data, such as feature values generated based audio processing of data received from a head-mounted microphone. The audio processing may detect noises associated with talking, eating, and drinking, and convert it to feature values to be provided to the machine learning-based model.

Using both TH_(ROI1) and IM_(ROI2) to detect the physiological response may confer some advantages in some embodiments. For example, there may be times when TH_(ROI1) and IM_(ROI2) provide complementing signals of a physiological response (e.g., due to their ability to measure manifestations of different physiological processes related to the physiological response). This can increase the accuracy of the detections. In one embodiment, in which the physiological response being detected is an emotional response, the computer may identify facial expressions from IM_(ROI2), and detect the emotional response of the user based on TH_(ROI1) and the identified facial expressions. For example, at least some of the feature values generated based on IM_(ROI2), which are used to detect the emotional response, are indicative of the facial expressions. Optionally, on average, detections of emotional responses based on both TH_(ROI1) and the identified facial expressions are more accurate than detections of the emotional responses based on either TH_(ROI1) or the identified facial expressions.

The following are some specific examples how IM_(ROI2) may be utilized to help make detections of a physiological response more accurate. In one example, ROI₁ and ROI₂ are on the mouth, and IM_(ROI2) are indicative of a change in a facial expression during a certain period that involves a transition from a facial expression in which the lips are in contact to a facial expression with an open mouth. Optionally, by utilizing IM_(ROI2) to detect the physiological response based on TH_(ROI1) taken during the certain period, the computer may be able attribute a change in TH_(ROI1) to opening the mouth rather than a change in the temperature of the lips.

In another example, ROI₁ and ROI₂ are on the nose and upper lip, and IM_(ROI2) are indicative of a change in a facial expression during a certain period that involves a transition from a neutral facial expression to a facial expression of disgust. Optionally, by utilizing IM_(ROI2) to detect the physiological response based on TH_(ROI1) taken during the certain period, the computer may be able attribute a change in TH_(ROI1) to a raised upper lip and wrinkled nose instead of a change in the temperature of the nose and upper lip.

In yet another example, ROI₁ and ROI₂ are on the user's forehead located about 1 cm above at least one of the user's eyebrows, and IM_(ROI2) are indicative of a change in a facial expression during a certain period that involves a transition from a neutral expression to a facial expression involving raised and/or lowered eyebrows (including middle-raised or middle-lowered eyebrows). Optionally, by utilizing IM_(ROI2) to detect the physiological response based on TH_(ROI1) taken during the certain period, the computer may be able attribute a change in TH_(ROI1) to raising and/or lowering the eyebrows instead of a change in the temperature of the forehead.

It is to be noted that there are various approaches known in the art for identifying facial expressions from images. While many of these approaches were originally designed for full-face frontal images, those skilled in the art will recognize that algorithms designed for full-face frontal images may be easily adapted to be used with images obtained using the inward-facing head-mounted visible-light cameras disclosed herein. For example, the various machine learning techniques described in prior art references may be applied to feature values extracted from images that include portions of the face from orientations that are not directly in front of the user. Furthermore, due to the closeness of VCAM to the face, facial features are typically larger in images obtained by the systems described herein. Moreover, challenges such as image registration and face tracking are vastly simplified and possibly non-existent when using inward-facing head-mounted cameras. The reference Zeng, Zhihong, et al. “A survey of affect recognition methods: Audio, visual, and spontaneous expressions.” IEEE transactions on pattern analysis and machine intelligence 31.1 (2009): 39-58, describes some of the algorithmic approaches that may be used for this task.

In some embodiments, TH_(ROI1) and IM_(ROI2) may provide different and even possibly contradicting indications regarding the physiological response. In particular, facial expressions may not always express how a user truly feels. For example, when in company of other people, a user may conceal his or her true feelings by making non-genuine facial expressions. However, at the same time, thermal measurements of the user's face may reveal the user's true emotions. Thus, a system that relies only on IM_(ROI2) to determine the user's emotional response may be mistaken at times, and using TH_(ROI1) can help make detections more accurate.

In one example, responsive to receiving a first set of TH_(ROI1) and IM_(ROI2) taken during a first period in which the user expressed a certain facial expression, the computer detects a first emotional response of the user. Additionally, responsive to receiving a second set of TH_(ROI1) and IM_(ROI2) taken during a second period in which the user expressed again the certain facial expression, the computer detects a second emotional response of the user, which is not the same as the first emotional response. The computer detected different emotional responses in this example because TH_(ROI1) of the first set are indicative of a first physiological response, while TH_(ROI1) of the second set are indicative of a second physiological response. Following are some more detailed examples of situations in which this may occur.

In one example, the first set includes IM_(ROI2) indicative of a facial expression that is a smile and TH_(ROI1) indicative of stress below a certain threshold, and the first emotional response detected by the computer is happiness. The second set in this example includes IM_(ROI2) indicative of a facial expression that is a smile and TH_(ROI1) indicative of stress above the certain threshold, and the second emotional response detected by the computer is discomfort.

In another example, the first set includes IM_(ROI2) indicative of a facial expression that is a neutral expression and TH_(ROI1) indicative of stress below a certain threshold, and the first emotional response detected by the computer is comfort. The second set includes IM_(ROI2) indicative of a facial expression that is neutral and TH_(ROI1) indicative of stress above the certain threshold, and the second emotional response detected by the computer is concealment.

In yet another example, the first set includes IM_(ROI2) indicative of a facial expression that is an expression of anger and TH_(ROI1) indicative of stress above a certain threshold, and the first emotional response detected by the computer is anger. The second set includes IM_(ROI2) indicative of a facial expression that is an expression of anger and TH_(ROI1) indicative of stress below the certain threshold, and the second emotional response detected by the computer is indicative of pretending to be angry.

The phenomenon of making different detections based on thermal measurements compared to the emotional response that is visible in a facial expression is illustrated in FIG. 44a and FIG. 44b . The illustrated figures include an HMS with CAM 514 and VCAM 515 that may cover portions of a cheek, mouth and/or nose. FIG. 44a illustrates a case in which the user's smiling face may be mistaken for happiness; however, the cold nose indicates that the user is in fact stressed. FIG. 44b illustrates a case in which the facial expression indicates that the user is in a neutral state; however, the warm nose indicates that the user is excited. FIG. 44a and FIG. 44b also illustrate a second CAM 516 and a second VCAM 517, which may be utilized in some embodiments, as described herein.

FIG. 45 illustrates one embodiment of a smartphone app that provides the user a feedback about how he/she looks to others. The illustrated app shows that the user was happy 96 time and angry 20 times. Because the purpose of this app is to measure how the user looks to others, the computer counts the facial expressions based on IM_(ROI2) without correcting the facial expressions according TH_(ROI1).

FIG. 46 illustrates one embodiment of a tablet app that provides the user a feedback about how he/she felt during a certain period (e.g., during the day, the week, or while being at a certain location). The illustrated app shows that the user felt sad 56 minutes and happy 135 minutes. Because the purpose of this app is to measure how the user feels (and not just how the user looks to others), the computer determines the user's emotional state based on a combined analysis of IM_(ROI2) and TH_(ROI1), as exemplified above.

In one embodiment, the system may include a second inward-facing head-mounted thermal camera (CAM2) that takes thermal measurements of a third ROI (TH_(ROI3)) on the face. Optionally, CAM2 weighs below 10 g and is physically coupled to the frame. Optionally, the center of ROI₁ is to the right of the center of the third region of interest (ROI₃), and the symmetric overlapping between ROI₁ and ROI₃ is above 50%. Optionally, to detect the physiological response, the computer accounts for facial thermal asymmetry, based on a difference between TH_(ROI1) and TH_(ROI3).

It is noted that the symmetric overlapping is considered with respect to the vertical symmetry axis that divides the face to the right and left portions. The symmetric overlapping between ROI₁ and ROI₃ may be observed by comparing the overlap between ROI₁ and a mirror image of ROI₃, where the mirror image is with respect to a mirror that is perpendicular to the front of the face and whose intersection with the face is along the vertical symmetry axis (which goes through the middle of the forehead and the middle of the nose).

Some examples of calculations that may be performed by the computer to account for thermal asymmetry include: (i) utilizing different thresholds to which TH_(ROI1) and TH_(ROI3) are compared; (ii) utilizing different reference time series to which TH_(ROI1) and TH_(ROI3) are compared; (iii) utilizing a machine learning-based model that provides different results for first and second events that involve the same average change in TH_(ROI1) and TH_(ROI3) with different extents of asymmetry in TH_(ROI1) and TH_(ROI3); and (iv) utilizing the asymmetry for differentiating between (a) temperature changes in TH_(ROI1) and TH_(ROI3) that are related to the physiological response and (b) temperature changes in TH_(ROI1) and TH_(ROI3) that are unrelated to the physiological response.

In one embodiment, the system may include a second inward-facing head-mounted visible-light camera (VCAM2) that takes images of a third ROI (IM_(ROI3)) on the face. Optionally, VCAM2 weighs below 10 g and is physically coupled to the frame. Optionally, VCAM and VCAM2 are located at least 0.5 cm to the right and to the left of the vertical symmetry axis that divides the face, respectively, and the symmetric overlapping between ROI₂ and ROI₃ is above 50%. Optionally, the computer detects the physiological response also based on IM_(ROI3). For example, the computer may generate some feature values based on IM_(ROI3), which may be similar to feature values generated based on IM_(ROI2), and utilizes the some feature values in the detection of the physiological response. In another example, the computer detects the physiological response based on the extent of symmetry between symmetric facial elements extracted from IM_(ROI2) and IM_(ROI3).

In some embodiments, IM_(ROI2) may include recognizable facial skin color changes (FSCC). FSCC are typically a result of changes in the concentration levels of hemoglobin and blood oxygenation under a user's facial skin, and are discussed in more detail elsewhere in this disclosure. In one embodiment, the computer calculates, based on IM_(ROI2), a value indicative of FSCC, and detects an emotional state of the user based on the calculated value. Optionally, on average, detections of the physiological response based on both TH_(ROI1) and FSCC are more accurate than detections of the physiological response based on either TH_(ROI1) or FSCC. In another embodiment, the computer generates feature values that are indicative of FSCC in IM_(ROI2), and utilizes a model to detect the physiological response based on the feature values. Optionally, at least some of the feature values are generated based on TH_(ROI1). Optionally, the model was trained based on samples, with each sample including feature values generated based on corresponding measurements of the user and a label indicative of the physiological response. Optionally, the label may be derived, for example, from analysis of the user's speech/writing, facial expression analysis, speech emotion analysis, and/or emotion extraction from analyzing galvanic skin response (GSR) and heart rate variability (HRV).

IM_(ROI2) may be utilized, in some embodiments, to detect occurrences of confounding factors that can affect the temperature on the face, but are unrelated to the physiological response being detected. Thus, occurrences of confounding factors can reduce the accuracy of detections of the physiological response based on thermal measurements (such as based on TH_(ROI1)). Detecting occurrences of the confounding factors described below (cosmetics, sweat, hair, inflammation and touching) may be done utilizing various image-processing and/or image-analysis techniques known in the art. For example, detecting occurrences of at least some of the confounding factors described below may involve a machine learning algorithm trained to detect the confounding factors, and/or comparing IM_(ROI2) to reference images that involve and do not involve the confounding factor (e.g., a first set of reference IM_(ROI2) in which makeup was applied to the face and a second set of reference IM_(ROI2) in which the face was bare of makeup).

The computer may utilize detection of confounding factors in various ways in order to improve the detection of the physiological response based on TH_(ROI1). In one embodiment, the computer may refrain from making a detection of the physiological response responsive to identifying that the extent of a certain confounding factor reaches a threshold. For example, certain physiological responses may not be detected if there is extensive facial hair on the face or extensive skin inflammation. In another embodiment, the model used to detect the physiological response may include a certain feature that corresponds to a certain confounding factor, and the computer may generate a certain feature value indicative of the extent of the certain confounding factor. Optionally, the model in this case may be trained on samples in which the certain feature has different values, such as some of the samples used to train the model are generated based on measurements taken while the certain confounding factor occurred, and other samples used to train the model were generated based on measurements taken while the certain confounding factor did not occur. In yet another embodiment, the computer may weight measurements based on the occurrence of confounding factors, such that measurements taken while certain confounding factors occurred, may be given lower weights than measurements taken while the certain confounding factor did not occur. Optionally, lower weights for measurements mean that they have a smaller influence on the detection of the physiological response than measurements with higher weights. The following are some examples of confounding factors that may be detected, in some embodiments, based on IM_(ROI2).

Some types of cosmetics (e.g., makeup and/or cream) may mask an ROI, affect the ROI's emissivity, and/or affect the ROI's temperature. Thus, taking into account cosmetics as a confounding factor may improve the system's ability to detect the physiological response. In one embodiment, the model was trained on: samples generated based on a first set of TH_(ROI1) and IM_(ROI2) taken after cosmetics were applied to a portion of the overlapping region between ROI₁ and ROI₂, and other samples generated based on a second set of TH_(ROI1) and IM_(ROI2) taken while the overlapping region was bare of cosmetics. Optionally, utilizing this model may enable the computer to account for presence of cosmetics on a portion of ROI₂.

Sweating may affect the ROI's emissivity. Thus, taking into account sweating as a confounding factor may improve the system's ability to detect the physiological response. In one embodiment, the model was trained on: samples generated from a first set of TH_(ROI1) and IM_(ROI2) taken while sweat was detectable on a portion of the overlapping region between ROI1 and ROI2, and additional samples generated from a second set of TH_(ROI1) and IM_(ROI2) taken while sweat was not detectable on the overlapping region. Optionally, utilizing this model may enable the computer to account for sweat on the overlapping region.

Dense hair may affect the ROI's emissivity, which may make the ROI appear, in thermal imaging, colder than it really is. Thus, taking into account hair density and/or hair length (both referred to as hair density) as a confounding factor may improve the system's ability to detect the physiological response. In one embodiment, the model was trained on: samples generated from a first set of TH_(ROI1) and IM_(ROI2) taken while hair density on a portion of the overlapping region between ROI₁ and ROI₂ was at a first level, and additional samples generated from a second set of TH_(ROI1) and IM_(ROI2) taken while hair density on the portion of the overlapping region between ROI₁ and ROI₂ was at a second level higher than the first level. Optionally, utilizing a model trained so may enable the computer to account for hair on the overlapping region.

In another embodiment, when the hair can be moved the system may request the user to move her hair in order to enable the thermal cameras to take correct measurements. For example, FIG. 50a illustrates a first case where the user's hair does not occlude the forehead. FIG. 50b illustrates a second case where the user's hair does occlude the forehead and thus the system requests the user to move the hair in order to enable correct measurements of the forehead.

Skin inflammations (which may include skin blemishes, acne, and/or inflammatory skin diseases) usually increases ROI temperature in a manner that is unrelated to the physiological response being detected. Thus, taking into account skin inflammation as a confounding factor may improve the system's ability to detect the physiological response. FIG. 48a illustrates heating of the ROI because of sinusitis, for which the system detects the physiological response (sinusitis). On the other hand, FIG. 48b illustrates heating of the same ROI because of acne, for which the system does detect sinusitis. In one embodiment, the model was trained on: samples generated from a first set of TH_(ROI1) and IM_(ROI2) taken while skin inflammation was detectable on a portion of the overlapping region between ROI₁ and ROI₂, and additional samples generated from a second set of TH_(ROI1) and IM_(ROI2) taken while skin inflammation was not detectable on the overlapping region. Optionally, utilizing a model trained so may enable the computer to account for skin inflammation on the overlapping region.

Touching the ROI may affect TH_(ROI) by increasing or decreasing the temperature at the touched region. Thus, touching the ROI may be considered a confounding factor that can make detections of the physiological response less accurate. In one embodiment, the model was trained on: samples generated from a first set of TH_(ROI1) and IM_(ROI2) taken while detecting that the user touches a portion of the overlapping region between ROI₁ and ROI₂, and additional samples generated from a second set of TH_(ROI1) and IM_(ROI2) taken while detecting that the user does not touch the overlapping region. Optionally, utilizing a model trained so may enables the computer to account for touching the overlapping region.

Throughout day-to-day activities, a user may make various facial movements that are unrelated to the physiological response being detected, and thus can negatively affect the thermal measurements taken by CAM. This can lead to measurements that may be incorrectly attributed to the physiological response. To address this issue, the computer may identify disruptive activities, such as talking, eating, and drinking, and utilize the identified disruptive activities in order to more accurately detect the physiological response. In one embodiment, the computer utilizes a machine learning-based approach to handle the disruptive activities. This approach may include (i) identifying, based on IM_(ROI2), occurrences of one or more of the disruptive activities, (ii) generating feature values based on the identified disruptive activities, and (iii) utilizing a machine learning-based model to detect the physiological response based on the feature values and feature values generated from TH_(ROI1).

In addition to detecting a physiological response, in some embodiments, the computer may utilize IM_(ROI2) to generate an avatar of the user (e.g., in order to represent the user in a virtual environment). Optionally, the avatar may express emotional responses of the user, which are detected based on IM_(ROI2). Optionally, the computer may modify the avatar to show synthesized facial expressions that are not manifested in the user's actual facial expressions, but the synthesized facial expressions correspond to emotional responses detected based on TH_(ROI1). Some of the various approaches that may be utilized to generate the avatar based on IM_(ROI2) are described in co-pending US patent publication 2016/0360970.

Contraction and relaxation of various facial muscles can cause facial tissue to slightly change its position and/or shape. Thus, facial movements can involve certain movements to ROIs. With thermal cameras that have multiple sensing elements (pixels), this can cause the ROI to move and be covered by various subsets of pixels as the user's face moves (e.g., due to talking/or making facial expressions). For example, smiling can cause the user's cheeks to move upwards. This can cause a thermal camera that covers a cheek to capture an ROI located on a cheek with a first set of pixels (from among the camera's pixels) when the user has a neutral expression, and to capture images of the ROI with a second set of pixels, when the user is smiling. In this example, on average, the pixels in the second set are likely to be located higher in the images than the pixels in the first set. To account for the possible movement of ROIs due to facial expressions, the computer may track locations of one or more facial landmarks in a series of IM_(ROI2), and utilize the locations to adjust TH_(ROI1). Facial landmarks are usually the most salient facial points on the face.

In one embodiment in which CAM comprises multiple sensing elements, which correspond to values of multiple pixels in TH_(ROI1), the computer may assign weights to the multiple pixels based on the locations of the one or more facial landmarks, which are determined based on IM_(ROI2). Assigning weights to pixels based on their location with respect to a facial landmark can be considered a form of selection of the pixels that cover the ROI based on the location of the landmark. In one example, the weights are assigned based on a function that takes into account the distance of each pixel from the locations of one or more facial landmarks and/or the relative position of each pixel with respect to the locations.

In another embodiment, the computer may generate certain feature values based on locations of one or more landmarks, which are determined based on analysis of IM_(ROI2). These certain feature values may be utilized in conjunction with other feature values (e.g., feature values generated based on TH_(ROI1)) to detect the physiological response using a machine learning-based model.

The following is a description of a method for detecting a physiological response based on measurements from CAM and VCAM. The steps described below may be performed by running a computer program having instructions for implementing the method. Optionally, the instructions may be stored on a computer-readable medium, which may optionally be a non-transitory computer-readable medium. In response to execution by a system including a processor and memory, the instructions cause the system to perform the following steps: In Step 1, taking thermal measurements of a first ROI (TH_(ROI1)) on the user's face using an inward-facing head-mounted thermal camera located at most 15 cm from the user's face. In Step 2, taking images of a second ROI (IM_(ROI2)) on the user's face with an inward-facing head-mounted visible-light camera located at most 15 cm from the user's face. Optionally, the first ROI (ROI₁) and the second ROI (ROI₂) overlap. In Step 3, generating feature values based on TH_(ROI1) and IM_(ROI2). And in Step 4, utilizing a model to detect the physiological response based on the feature values. Optionally, the model was trained based on previous TH_(ROI1) and IM_(ROI2) taken on different days.

In one embodiment, the physiological response is an emotional response, and the method optionally includes the following steps: calculating, based on IM_(ROI2), a value indicative of facial skin color changes (FSCC), and utilizing the value indicative of FSCC to generate at least one of the feature values used to detect the physiological response in Step 4.

In another embodiment, generating the feature values in Step 3 involves generating, based on IM_(ROI2), feature values indicative of an occurrence of one or more of the following confounding factors on a portion of the overlapping region between ROI₁ and ROI₂: a presence of cosmetics, a presence of sweat, a presence of hair, and a presence of skin inflammation.

The following is a description of a system that detects a physiological response based on an inward-facing head-mounted thermal camera (CAM_(in)), an outward-facing head-mounted thermal camera (CAM_(out)), and a computer. CAM_(out) measures the environment and generates data indicative of confounding factors, such as direct sunlight or air conditioning. Accounting for confounding factors enables the system to more accurately detect the physiological response compared to a system that does not account for these confounding factors. Optionally, CAM_(in) and/or CAM_(out) are physically coupled to a frame worn on a user's head, such as a frame of a pair of eyeglasses or an augmented reality device. Optionally, each of CAM_(in) and CAM_(out) weighs below 5 g and is located less than 15 cm from the user's face.

CAM_(in) takes thermal measurements of an ROI (TH_(ROI)) on the user's face. Optionally, CAM_(in) does not occlude the ROI. In one example, the ROI includes a region on the forehead and the physiological response involves stress, a headache, and/or a stroke. In another example, the ROI includes a region on the nose and the physiological response is an allergic reaction.

CAM_(out) takes thermal measurements of the environment (TH_(ENV)). Optionally, CAM_(out) does not occlude the ROI. Optionally, the angle between the optical axes of CAM_(in) and CAM_(out) is at least 45°, 90°, 130°, 170°, or 180°. Optionally, the field of view (FOV) of CAM_(in) is larger than the FOV of CAM_(out) and/or the noise equivalent differential temperature (NEDT) of CAM_(in) is lower than NEDT of CAM_(out). In one example, CAM_(in) has a FOV smaller than 80° and CAM_(out) has a FOV larger than 80°. In another example, CAM_(in) has more sensing elements than CAM_(out) (e.g., CAM_(in) has at least double the number of pixels as CAM_(out)).

In one embodiment, CAM_(in) and CAM_(out) are based on sensors of the same type with similar operating parameters. Optionally, CAM_(in) and CAM_(out) are located less than 5 cm or 1 cm apart. Having sensors of the same type, which are located near each other, may have an advantage of having both CAM_(in) and CAM_(out) be subject to similar inaccuracies resulting from heat conductance and package temperature. In another embodiment, CAM_(in) and CAM_(out) may be based on sensors of different types, with different operating parameters. For example, CAM_(in) may be based on a microbolometer FPA while CAM_(out) may be based on a thermopile (that may be significantly less expensive than the microbolometer).

FIG. 51a illustrates one embodiment of the system that includes inward-facing and outward-facing head-mounted thermal cameras on both sides of the frame. In this illustration, CAM_(in) is the inward-facing thermal camera 12, which takes thermal measurements of ROI 13, and CAM_(out) is the outward-facing thermal camera 62. Arc 64 illustrates the larger FOV of CAM_(out) 62, compared to the FOV of CAM_(in) that covers ROI 13. The illustrated embodiment includes a second head-mounted thermal camera 10 (CAM_(in2)) on the right side of the frame, which takes thermal measurements of ROI 11, and a second outward-facing head-mounted thermal camera 63 (CAM_(out2)). FIG. 51b illustrates receiving an indication on a GUI (on the illustrated laptop) that the user is not monitored in direct sunlight. Cameras 520 and 521 are the outward-facing head-mounted thermal cameras.

The computer detects a physiological response based on TH_(ROI) and TH_(ENV). Optionally, TH_(ENV) are utilized to account for at least some of the effect of heat transferred from the environment to the ROI (and not due to the user's physiological response). Thus, on average, detections of the physiological response based on TH_(ROI) and TH_(ENV) may be more accurate than detections of the physiological response based on TH_(ROI) without TH_(ENV).

There are various ways in which the computer may utilize TH_(ENV) to increase the accuracy of detecting the physiological response. In one embodiment, the computer generates feature values based on a set of TH_(ROI) and TH_(ENV), and utilizes a machine learning-based model to detect, based on the feature values, the physiological response. By utilizing TH_(ENV) to generate one or more of the feature values, the computer may make different detections of the physiological response based on similar TH_(ROI) that are taken in dissimilar environments. For example, responsive to receiving a first set of measurements in which TH_(ROI) reaches a first threshold while TH_(ENV) does not reach a second threshold, the computer detects the physiological response. However, responsive to receiving a second set of measurements in which TH_(ROI) reaches the first threshold while TH_(ENV) reaches the second threshold, the computer does not detect the physiological response. Optionally, TH_(ENV) reaching the second threshold indicates that the user was exposed to high infrared radiation that is expected to interfere with the detection.

In another embodiment, the computer may utilize TH_(ENV) for the selection of values that are appropriate for the detection of the physiological response. In one example, the computer may select different thresholds (to which TH_(ROI) are compared) for detecting the physiological response. In this example, different TH_(ENV) may cause the computer to use different thresholds. In another example, the computer may utilize TH_(ENV) to select an appropriate reference time series (to which TH_(ROI) may be compared) for detecting the physiological response. In yet another example, the computer may utilize TH_(ENV) to select an appropriate model to utilize to detect the physiological response based on the feature values generated based on TH_(ROI).

In still another embodiment, the computer may normalize TH_(ROI) based on TH_(ENV). In one example, the normalization may involve subtracting a value proportional to TH_(ENV) from TH_(ROI), such that the value of the temperature at the ROI is adjusted based on the temperature of the environment at that time and/or in temporal proximity to that time (e.g., using an average of the environment temperature during the preceding minute). Additionally or alternatively, the computer may adjust weights associated with at least some TH_(ROI) based on TH_(ENV), such that the weight of measurements from among TH_(ROI) that were taken during times the measurements of the environment indicated extreme environmental temperatures is reduced.

In yet another embodiment, responsive to determining that TH_(ENV) represent an extreme temperature (e.g., lower than 5° C., higher than 35° C., or some other ranges deemed inappropriate temperatures), the computer may refrain from performing detection of the physiological response. This way, the computer can avoid making a prediction that is at high risk of being wrong due to the influence of the extreme environmental temperatures. In a similar manner, instead of determining that TH_(ENV) represent an extreme temperature, the computer may determine that the difference between TH_(ROI) and TH_(ENV) are not in an acceptable range (e.g., there is a difference of more than 15° C. between the two), and refrain from making a detection of the physiological response in that event.

The following examples describe ways to use TH_(ENV) to detect the physiological response based on TH_(ROI). In one example, the computer detects the physiological response based on a difference between TH_(ROI) and TH_(ENV), which enables the system to operate well in an uncontrolled environment that does not maintain environmental temperature in a range below ±1° C. and does not maintain humidity in a range below ±3%. In another example, the computer detects the physiological response by performing the following steps: calculating a temperature difference between TH_(ROI) and TH_(ENV) taken at time x (ΔT_(x)), calculating a temperature difference between TH_(ROI) and TH_(ENV) taken at time y (ΔT_(y)), and detecting the physiological response based on a difference between ΔT_(X) and ΔT_(y). Optionally, detecting the physiological response is based on the difference between ΔT_(X) and ΔT_(y) reaching a predetermined threshold. Optionally, the predetermined threshold is selected from a threshold in the time domain, and/or a threshold in the frequency domain. Optionally, the magnitude of the difference between ΔT_(X) and ΔT_(y) is indicative of an extent of the physiological response. It is noted that sentences such as “calculating a difference between M and N” or “detecting a difference between M and N” are intended to cover any function that is proportional to the difference between M and N.

Because the FOV of CAM_(out) is limited and the responsivity of CAM_(out) decreases when drawing away from the optical axis, it may be beneficial to utilize two or more CAM_(out) pointed at different angles.

In one embodiment, the system may include a second outward-facing head-mounted thermal camera (CAM_(out2)), which takes thermal measurements of the environment (TH_(ENV2)). Optionally, there is an angle of at least 30° between the optical axes of CAM_(out) and CAM_(out2). Utilizing two or more outward-facing head-mounted thermal cameras such as CAM_(out) and CAM_(out2) can help identify cases in which there is a directional environmental interference (e.g., sunlight coming from a certain direction). In some cases, such a directional interference can lead to refraining from making a detection of the physiological response. For example, responsive to receiving a first set of measurements in which TH_(ROI) reach a first threshold while the difference between TH_(ENV) and TH_(ENV2) does not reach a second threshold, the computer detects the physiological response. However, responsive to receiving a second set of measurements in which TH_(ROI) reach the first threshold while the difference between TH_(ENV) and TH_(ENV2) reaches the second threshold, the computer does not detect the physiological response. Optionally, the computer detects the physiological response based on a difference between TH_(ROI), TH_(ENV), and TH_(ENV2), while taking into account the angle between the optical axes of CAM_(out) and CAM_(out2) and a graph of responsivity as function of the angle from the optical axes of each of CAM_(out) and CAM_(out2).

In another embodiment, CAM_(in) and CAM_(out) are located to the right of the vertical symmetry axis that divides the user's face, and the ROI is on the right side of the face. Optionally, the system includes a second inward-facing head-mounted thermal camera (CAM_(in2)) and a second outward-facing head-mounted thermal camera (CAM_(out2)) located to the left of the vertical symmetry axis. CAM_(in2) takes thermal measurements of a second ROI (TH_(ROI2)) on the left side of the face, and does not occlude the second ROI (ROI₂). CAM_(or)t₂ takes thermal measurements of the environment (TH_(ENV2)) that is more to the left relative to TH_(ENV). In this embodiment, the computer detects the physiological response also based on TH_(ROI2) and TH_(ENV2).

In still another embodiment, the optical axes of CAM_(in) and CAM_(out) are above the Frankfort horizontal plane, and the system further includes a second inward-facing head-mounted thermal camera (CAM_(in2)) and a second outward-facing head-mounted thermal camera (CAM_(out2)), located such that their optical axes are below the Frankfort horizontal plane, which take thermal measurements TH_(ROI2) and TH_(ENV2), respectively. In this embodiment, the computer detects the physiological response also based on TH_(ROI2) and TH_(ENV2).

Optionally, the computer detects the physiological response by performing at least one of the following calculations: (i) when the difference between TH_(ENV) and TH_(ENV2) reaches a threshold, the computer normalizes TH_(ROI) and TH_(ROI2) differently against thermal interference from the environment, (ii) when TH_(ENV) does not reach a predetermined threshold for thermal environmental interference, while TH_(ENV2) reaches the predetermined threshold, the computer assigns TH_(ROI) a higher weight than TH_(ROI2) for detecting the physiological response, and (iii) the computer generates feature values based on TH_(ROI), TH_(ENV), TH_(ENV2) and optionally TH_(ROI2) and utilizes a model to detect, based on the feature values, the physiological response. Optionally, the model was trained based on a first set of TH_(ROI), TH_(ROI2), TH_(ENV) and TH_(ENV2) of one or more users taken while the one or more users had the physiological response, and a second set of TH_(ROI), TH_(ROI2), TH_(ENV) and TH_(ENV2) of the one or more users taken while the one or more users did not have the physiological response.

In addition to having one or more CAM_(out), or instead of having the one or more CAM_(out), some embodiments may include a sensor that may be used to address various other confounding factors, such as user movements and wind, which are discussed below. Optionally, the sensor is coupled to a frame worn on the user's head. An example of such a sensor is sensor 68 in FIG. 51 a.

In one embodiment, the sensor takes measurements (denoted m_(conf)) that are indicative of an extent of the user's activity, an orientation of the user's head, and/or a change in a position of the user's body. For example, the sensor may be (i) a movement sensor that is physically coupled to a frame worn on the user's head, or coupled to a wearable device worn by the user, (ii) a visible-light camera that takes images of the user, and/or (iii) an active 3D tracking device that emits electromagnetic waves and generates 3D images based on received reflections of the emitted electromagnetic waves. Optionally, the computer detects the physiological response also based on m_(conf). In one example, the computer may refrain from detecting the physiological response if m_(conf) reaches a threshold (which may indicate the user was very active which causes an increase in body temperature). In another example, the computer generates feature values based on TH_(ROI), TH_(ENV), and m_(conf) and utilizes a model to detect the physiological response based on the feature values. Optionally, the model was trained based on previous TH_(ROI), TH_(ENV), and m_(conf) taken while the user had different activity levels. For example, the model may be trained based on: a first set of previous TH_(ROI), TH_(ENV), and m_(conf) taken while the user was walking or running, and a second set of previous TH_(ROI), TH_(ENV), and m_(conf) taken while the user was sitting or standing.

FIG. 53 illustrates an elderly person whose facial temperature increases as a result of bending the head down towards the floor. In this example, the system receives an indication of the user's action via the sensor (e.g., one or more gyroscopes) and consequently refrains from erroneously detecting certain physiological responses, since the increase in temperature may be attributed to the person being bent over. In one embodiment, a sensor provides indications indicative of bending the head down above a certain degree from the normal to earth, where bending the head down above the certain degree is expected to cause a change in TH_(ROI). The computer generates feature values based on TH_(ROI), TH_(ENV), and m_(conf), and utilizes a model to detect the physiological response based on the feature values. The model was trained based on: a first set of previous TH_(ROI), TH_(ENV), and m_(conf) taken while a user was bending the head down above the certain degree, and a second set of previous TH_(ROI), TH_(ENV), and m_(conf) taken while the user was not bending the head down above the certain degree.

In another embodiment, the sensor may be an anemometer that is physically coupled to a frame worn on the user's head, is located less than 15 cm from the face, and provides a value indicative of a speed of air directed at the face (m_(wind)). Optionally, the computer detects the physiological response also based on m_(wind). In one example, the computer refrains from detecting the physiological response if m_(wind) reaches a threshold (which may indicate that the user was in an environment with strong wind that may excessively cool regions on the face). In another example, the computer generates feature values based on TH_(ROI), TH_(ENV), and m_(wind) and utilizes a model to detect, based on the feature values, the physiological response. FIG. 52 illustrates a case in which a user receives an indication that she is not being monitored in a windy environment. Optionally, the model was trained based on previous TH_(ROI), TH_(ENV), and m_(wind) taken while a user was in different environments. For example, the model may be trained based on: a first set of previous TH_(ROI), TH_(ENV), and m_(wind) taken while being indoors, and a second set of previous TH_(ROI), TH_(ENV), and m_(wind) taken while being outdoors.

The following is a method for detecting a physiological response while taking into account a confounding factor that involves environmental thermal interferences (e.g., direct sunlight). Having different environmental conditions may cause a system such as the one illustrated in FIG. 51a to behave differently, as shown in the steps below. The steps described below may be performed by running a computer program having instructions for implementing the method. Optionally, the instructions may be stored on a computer-readable medium, which may optionally be a non-transitory computer-readable medium. In response to execution by a system including a processor and memory, the instructions cause the system to perform the following steps: In Step 1, taking thermal measurements of a region of interest (TH_(ROI)) on a user's face utilizing an inward-facing head-mounted thermal camera (CAM_(in)) worn by the user. In step 2, taking thermal measurements of the environment (TH_(ENV)) utilizing an outward-facing head-mounted thermal camera (CAM_(out)) worn by the user. In step 3, generating feature values based on TH_(ROI) and TH_(ENV). And in step 4, utilizing a machine learning-based model to detect the physiological response based on the feature values.

The method may optionally further include the following steps: taking a first set of TH_(ROI) (first TH_(ROI)), where the first set of TH_(ROI) reach a first threshold; taking a first set of TH_(ENV) (first TH_(ENV)), where the first set of TH_(ENV) do not reach a second threshold; detecting, based on the first set of TH_(ROI) and the first set of TH_(ENV), that the user had the physiological response; taking a second set of TH_(ROI), where the second set of TH_(ROI) reach the first threshold; taking a second set of TH_(ENV), where the second set of TH_(ENV) reach the second threshold; and detecting, based on the second set of TH_(ROI) and the second set of TH_(ENV), that the user did not have the physiological response. Optionally, the method further includes: taking a third set of TH_(ROI), where the third set of TH_(ROI) do not reach the first threshold; taking a third set of TH_(ENV), where the third set of TH_(ENV) do not reach the second threshold; and detecting, based on the third set of TH_(ROI) and the third set of TH_(ENV), that the user did not have the physiological response.

The following is a description of a system for detecting a physiological response, which includes a CAM and a sensor. The sensor provides measurements indicative of times at which the user touches the face. Touching the face can warm certain regions of the face, and the system may utilize these measurements in order to account for such cases. Thus, the system may more accurately detect the physiological response compared to systems that do not account for touching of the face.

CAM is worn on the user's head and takes thermal measurements of an ROI (TH_(ROI)) on the user's face. Optionally, the system includes a frame to which CAM and the sensor may be physically coupled. Optionally, CAM is located less than 15 cm from the face and/or weighs below 10 g.

The sensor provides measurements (M) indicative of times at which the user touches the ROI. The user may touch the ROI using/with a finger, the palm, a tissue or a towel held by the user, a makeup-related item held by the user, and/or a food item eaten by the user. Touching the ROI may affect TH_(ROI) by increasing or decreasing the temperature at the touched region. Thus, touching the ROI may be considered a confounding factor that can make detections of the physiological response by a computer less accurate. M may include values measured by the sensor and/or results of processing of values measured by the sensor. Various types of sensors may be utilized in different embodiments to generate M, such as: a visible-light camera (where the computer uses image processing to identify touching the ROI), a miniature radar (such as low-power radar operating in the range between 30 GHz and 3,000 GHz, where the computer uses signal processing of the reflections to identify touching the ROI), a miniature active electro-optics distance measurement device, and/or an ultrasound sensor.

In some embodiments, the sensor may be unattached to a frame worn on the user's head. For example, the sensor may include a visible-light camera mounted to an object in the user's environment (e.g., a laptop), and may normally located at a distance greater than 20 cm from the user's face. Optionally, the computer may utilize M to determine when it is likely (but not necessarily certain) that the user touched the face. In one example, the sensor includes a movement-measuring device embedded in a bracelet, and the computer increases the probability for a physical contact with the face when the user's hand is estimated to be at face level and/or close to the face. In another example, the sensor includes an altimeter embedded in a bracelet, and the computer increases the probability for an event of physical contact with the face when the user's hand is estimated to be at face level.

FIG. 49a and FIG. 49b illustrate one embodiment of a system that provides indications when the user touches his/her face. The system includes a frame 533, head-mounted sensors (530, 531, 532) able to detect touching the face, and head-mounted thermal cameras (534, 535, 536, 537). Optionally, the head-mounted sensors are visible-light cameras that take images of the ROIs. Head-mounted sensor 530 captures an ROI above the frame, and head-mounted sensors 531 and 532 capture ROIs below the frame. Hot spot 538, which is measured by the thermal camera 534, was caused by touching the forehead and is unrelated to the physiological response being detected. Upon detecting touching of the ROI, the computer may use the associated thermal measurements differently than it would use had the touching not been detected. Additionally or alternatively, a user interface may provide an indication that touching the ROI hinders the detection of the physiological response.

The computer detects the physiological response based on TH_(ROI) and M. Optionally, since the computer utilizes M to account, at least in part, for the effect of touching the face, on average, detections of the physiological response based on TH_(ROI) and M are more accurate than detections of the physiological response based on TH_(ROI) without M. The computer may utilize TH_(ROI) in various ways in order to detect the physiological response, such as comparing one or more values derived from TH_(ROI) to a threshold and/or comparing TH_(ROI) to a reference time series.

Another approach that may be utilized involves a machine learning-based model. In one embodiment, the computer generates feature values based on TH_(ROI) and M, and utilizes the model to detect, based on the feature values, the physiological response. By utilizing M to generate one or more of the feature values, the computer may make different detections of the physiological response based on similar TH_(ROI) that are taken while there are different extents of touching the ROI. For example, responsive to receiving a first set of measurements in which TH_(ROI) reaches a threshold, while M indicate that there was no touching of the ROI, the computer detects the physiological response. However, responsive to receiving a second set of measurements in which TH_(ROI) reaches the threshold, but M indicate that the user touched the ROI, the computer does not detect the physiological response. Optionally, the model is trained based on samples, each comprising: (i) feature values generated based on TH_(ROI) taken while M indicates touching the ROI, and (ii) a corresponding label indicative of an extent of the physiological response. Optionally, the samples include: a first set of samples with labels corresponding to having the physiological response, which are generated based on M indicating that the ROI was not touched, and a second set of samples with labels corresponding to not having the physiological response, which are generated based on M indicating that the ROI was touched. Optionally, the samples comprise: a third set of samples with labels corresponding to having the physiological response, which are generated based on M indicating that the ROI was touched, and/or a fourth set of samples with labels corresponding to not having the physiological response, which are generated based on M indicating that the ROI was not touched.

M may be utilized by the computer in order to decrease the chance of making incorrect detections of the physiological response. In one embodiment, the computer utilizes, for the detection of the physiological response, TH_(ROI) taken at times in which M are not indicative of touching the ROI. In this embodiment, the computer does not utilize, for the detection of the physiological response, TH_(ROI) taken at times in which M are indicative of touching the ROI. In another embodiment, the computer does not utilize, for the detection of the physiological response, TH_(ROI) taken during at least one of the following intervals starting after M indicate that the user touched the ROI: 0-10 seconds, 0-30 second, 0-60 second, 0-180 seconds, and 0-300 seconds. In yet another embodiment, the computer attributes, for the detection of the physiological response, a smaller weight to TH_(ROI) taken during a certain interval starting after M indicate that the user touched the ROI, compared to a weight attributed to TH_(ROI) taken at times shortly before M indicate that the user touched the ROI. Optionally, the certain interval includes at least one of the following durations: 10-30 second, 30-60 second, 60-120 seconds, and 120-300 seconds. Optionally, the higher the weight attributed to a measurement, the more it influences calculations involved in the detection of the physiological response.

In one embodiment, the system optionally includes a user interface (UI) which notifies the user about touching the ROI. Optionally, this notification is in lieu of notifying extent of the physiological response corresponding to the time the user touched the ROI. The notification may be delivered to the user using a sound, a visual indication on a head-mounted display, and/or a haptic feedback. Optionally, the UI includes a screen of an HMS (e.g., a screen of an augmented reality headset), a screen of a device carried by the user (e.g., a screen of a smartphone or a smartwatch), and/or a speaker (e.g., an earbud or headphones). Optionally, the computer identifies that the duration and/or extent of touching the face reached a threshold, and then commands the UI to alert the user that an accurate detection of the physiological response cannot be made as long as the touching continues.

In one embodiment, the sensor includes a visible-light camera and/or a near-infrared camera, the system is powered by a battery, and the system may operate in a state belonging to a set comprising first and second states. While operating in the first state, the system checks on a regular basis whether the user touches the ROI. While operating in the second state, the system checks whether the user touches the ROI in response to detecting abnormal TH_(ROI). Optionally, the system consumes less power while operating in the second state compared to the power it consumes while operating in the first state.

In one embodiment, the measurements taken by the sensor are further indicative of an angular position of CAM relative to the ROI while the frame is still worn on the head, and the computer detects the physiological response also based on the angular position. Optionally, the measurements of the angular position are utilized to account for instances in which the frame has moved, and consequently CAM captures a region that only overlaps, or does not overlap at all, with the intended ROI. Optionally, the computer is able to detect changes below 5° in the angular position, which may also influence TH_(ROI). Thus, on average, detections of the physiological response based on TH_(ROI) and the angular position are more accurate compared to detections of the physiological responses based on TH_(ROI) without the angular position, while the frame is still worn on the head.

In a first example, responsive to the angular position of CAM relative to the ROI reaching a predetermined threshold, the computer refrains from detecting the physiological response and/or alerts the user.

In a second example, the computer generates feature values based on TH_(ROI) and the angular position, and utilizes a model to detect the physiological response based on the feature values. Optionally, the model was trained based on data comprising TH_(ROI) collected while CAM was at different distances and/or angular positions relative to the ROI. Thus, the model may account, in its parameters, for various effects that the distance and/or orientation of CAM may have on TH_(ROI) in order to more accurately detect the physiological response.

In a third example, the sensor includes a visible-light camera that takes images of a region on the user's face, and the computer calculates the angular position of the visible-light camera relative to the face based on analyzing the images, and then calculates the angular position of CAM relative to the ROI based on a predetermined transformation between the angular position of the visible-light camera relative to the face and the angular position of CAM relative to the ROI.

In a fourth example, the sensor includes a transceiver of electromagnetic waves, and the computer calculates the angular position of the transceiver relative to the face based on signal processing of the reflections from the face, and then calculates the angular position of CAM relative to the ROI based on a predetermined transformation between the angular position of the transceiver relative to the face and the angular position of CAM relative to the ROI.

The following method for detecting a physiological response may be used, in some embodiments, by the system described above, which detects a physiological response while taking into account a confounding factor such as touching the face. The steps described below may be performed by running a computer program having instructions for implementing the method. Optionally, the instructions may be stored on a computer-readable medium, which may optionally be a non-transitory computer-readable medium. In response to execution by a system including a processor and memory, the instructions cause the system to perform the following steps: In Step 1, taking thermal measurements of an ROI (TH_(ROI)) on a user's face using an inward-facing head-mounted thermal camera. In Step 2, taking, utilizing a sensor, measurements (M) indicative of times at which the user touches the ROI. Touching the ROI may affect TH_(ROI), for example by increasing the temperatures at the ROI (which may increase the values of TH_(ROI)). The sensor may be a head-mounted sensor or a sensor that is not head-mounted. And in Step 3, detecting the physiological response based on TH_(ROI) and M. For example, the detection may be performed by the computer, as described above. On average, detections of the physiological response based on TH_(ROI) and M are more accurate compared to detections of the physiological response based on TH_(ROI) without M.

Optionally, the method further includes the following steps: generating feature values based on TH_(ROI) and M, and utilizing a model for detecting the physiological response based on the feature values. Optionally, the model was trained based on samples, each comprising: (i) feature values generated based on previous TH_(ROI) taken while M indicates touching the ROI, and (ii) a corresponding label indicative of an extent of the physiological response. Optionally, the samples include: a first set of samples with labels corresponding to having the physiological response, which are generated based on M indicating that the ROI was not touched, and a second set of samples with labels corresponding to not having the physiological response, which are generated based on M indicating that the ROI was touched.

Optionally, M are further indicative of angular position of CAM relative to the ROI, while the frame is still worn on the head. And the method further includes a step of detecting the physiological response also based on the angular position. On average, detections of the physiological response based on TH_(ROI) and the angular position are more accurate compared to detections of the physiological responses based on TH_(ROI) without the angular position, while the frame is still worn on the head.

The following is a description of a system that detects a physiological response while taking into account a consumption of a confounding substance. When a person consumes a confounding substance, it may affect thermal measurements of an ROI (TH_(ROI)) on the person's face. The affect to TH_(ROI) can be attributed to various physiological and/or metabolic processes that may ensue following the consumption of the confounding substance, which can result (amongst possibly other effects) in a raising or decreasing of the temperature at the ROI in a manner that is unrelated to the physiological response being detected. Thus, embodiments of this system utilize indications indicative of consumption of a confounding substance (such as medication, an alcoholic beverage, a caffeinated beverage, and/or a cigarette) to improve the system's detection accuracy. In one embodiment, the system includes a CAM and a computer.

CAM is worn on the user's head and takes thermal measurements of an ROI (TH_(ROI)) on the user's face. Optionally, the system includes a frame to which CAM and the device are physically coupled. Optionally, CAM is located less than 15 cm from the face and/or weighs below 10 g.

In different embodiments, the ROI may cover different regions on the face and CAM may be located at different locations on a frame worn on the user's head and/or at different distances from the user's face. In one embodiment, the ROI is on the forehead, and CAM is physically coupled to an eyeglasses frame, located below the ROI, and does not occlude the ROI. Optionally, the physiological response detected in this embodiment is stress, a headache, and/or a stroke. In another embodiment, the ROI is on the periorbital area, and CAM is located less than 10 cm from the ROI. Optionally, the physiological response detected in this embodiment is stress. In yet another embodiment, the ROI is on the nose, and CAM is physically coupled to an eyeglasses frame and is located less than 10 cm from the face. Optionally, the physiological response detected in this embodiment is an allergic reaction. In still another embodiment, the ROI is below the nostrils, and CAM: is physically coupled to an eyeglasses frame, located above the ROI, and does not occlude the ROI. Optionally, the ROI covers one or more areas on the upper lip, the mouth, and/or air volume(s) through which the exhale streams from the nose and/or mouth flow, and the physiological response detected in this embodiment is a respiratory parameter such as the user's breathing rate.

The computer may receive, from a device, an indication indicative of consuming a confounding substance that is expected to affects TH_(ROI), such as an alcoholic beverage, a medication, caffeine, and/or a cigarette. Various types of devices may be utilized in different embodiments in order to identify consumption of various confounding substances.

In one embodiment, the device includes a visible-light camera that takes images of the user and/or the user's environment. Optionally, the visible-light camera is a head-mounted visible-light camera having in its field of view a volume that protrudes out of the user's mouth. Optionally, the computer identifies a consumption of the confounding substance based on analyzing the images. In one example, the visible-light camera may belong to a camera-based system such as OrCam (http://www.orcam.com/), which is utilized to identify various objects, products, faces, and/or recognize text. In another example, images captured by the visible-light camera may be utilized to determine the nutritional composition of food a user consumes. Such an approach in which images of meals are utilized to generate estimates of food intake and meal composition, is described in Noronha, et al., “Platemate: crowdsourcing nutritional analysis from food photographs”, Proceedings of the 24th annual ACM symposium on User interface software and technology, ACM, 2011. Additional examples of how a visible-light camera may be utilized to identify consumption of various substances is given in U.S. Pat. No. 9,053,483 (Personal audio/visual system providing allergy awareness) and in U.S. Pat. No. 9,189,021 (Wearable food nutrition feedback system).

In another embodiment, the device includes a microphone that records the user, and the computer identifies a consumption of the confounding substance utilizing a sound recognition algorithm operated on a recording of the user. Optionally, the sound recognition algorithm comprises a speech recognition algorithm configured to identify words that are indicative of consuming the confounding substance.

In yet another embodiment, the confounding substance is a medication, and the device includes a pill dispenser that provides an indication indicating that the user took a medication, and/or a sensor-enabled pill that includes an ingestible signal generator coupled to a medication that is configured to generate a body-transmissible signal upon ingestion by a user, such as the sensor-enabled pill described in PCT publication WO/2016/129286. Optionally, the indication indicates the type of medication and/or its dosage.

In still another embodiment, the device is a refrigerator, a pantry, and/or a serving robot. Optionally, the device provides an indication indicative of the user taking an alcoholic beverage and/or a food item.

In yet another embodiment, the device has an internet-of-things (IoT) capability through which the indication is provided to the system. For example, the device may be part of a “smart device” with network connectivity.

And in yet another embodiment, the device belongs to a user interface that receives an indication from the user or/or a third party about the consuming of the confounding substance.

Due to various metabolic and/or other physiological processes, consumption of a confounding substance may affect TH_(ROI). For example, many drugs are known to act on the hypothalamus and other brain centers involved in controlling the body's thermoregulatory system. Herein, stating “the confounding substance affects TH_(ROI)” means that consuming the confounding substance leads to a measurable change of the temperature at the ROI, which would likely not have occurred had the confounding substance not been consumed. Similarly, a time in which “confounding substance did not affect TH_(ROI)” is a time that occurs after at least a certain duration has elapsed since the confounding substance was last consumed (or was not consumed at all), and the consumption of the confounding substance is no longer expected to have a noticeable effect on the ROI temperature. This certain duration may depend on factors such as the type of substance, the amount consumed, and previous consumption patterns. For example, the certain duration may be at least: 30 minutes, two hours, or a day.

The duration of the effect of a confounding substance may vary between substances, and may depend on various factors such as the amount of substance, sex, weight, genetic characteristics, and the user's state. For example, consumption of alcohol on an empty stomach often has a greater effect on TH_(ROI) than consumption of alcohol with a meal. Some confounding substances may have a long-lasting effect, possibly throughout the period they are taken. For example, hormonal contraceptives can significantly alter daily body temperatures. Other confounding factors, such as caffeine and nicotine, may have shorter lasting effects, typically subsiding within less than an hour or two following their consumption.

The computer detects the physiological response based on TH_(ROI) and the indication indicative of consuming the confounding substance. In one embodiment, the computer refrains from detecting the physiological response within a certain window during which the confounding substance affected the user (e.g., an hour, two hours, or four hours). In another embodiment, the computer utilizes a model, in addition to TH_(ROI) and the indication, to detect whether the user had the physiological response during the time that a consumed confounding substance affected TH_(ROI). Optionally, the computer detects the physiological response by generating feature values based on TH_(ROI) and the indication (and possibly other sources of data), and utilizing the model to calculate, based on the feature values, a value indicative of the extent of the physiological response. Optionally, the feature values include a feature value indicative of one or more of the following: the amount of the consumed confounding substance, the dosage of the consumed confounding substance, the time that has elapsed since the confounding substance had last been consumed, and/or the duration during which the confounding factor has been consumed (e.g., how long the user has been taking a certain medication).

In one embodiment, the model was trained based on data collected from the user and/or other users, which includes TH_(ROI), the indications described above, and values representing the physiological response corresponding to when TH_(ROI) were taken. Optionally, the data is used to generate samples, with each sample comprising feature values and a label. The feature values of each sample are generated based on TH_(ROI) taken during a certain period and an indication indicating whether a confounding substance affected TH_(ROI) taken during the certain period. The label of the sample is generated based on one or more of the values representing the physiological response, and indicates whether (and optionally to what extent) the measured user had the physiological response during the certain period. Optionally, the data used to train the model reflects both being affected and being unaffected by the confounding substance. For example, the data used to train the model may include: a first set of TH_(ROI) taken while the confounding substance affected TH_(ROI), and a second set of TH_(ROI) taken while the confounding substance did not affect TH_(ROI). Optionally, each of the first and second sets comprises at least some TH_(ROI) taken while the measured user had the physiological response and at least some TH_(ROI) taken while the measured user did not have the physiological response.

Using the indications (indicative of the user consuming a confounding substance) may lead to cases where the detection of the physiological response depends on whether the confounding substance was consumed. In one example, in which the physiological response is detected when TH_(ROI) reach a threshold, the computer's detection behavior may be as follows: the computer detects the physiological response based on first TH_(ROI) for which there is no indication indicating that the first TH_(ROI) were affected by a consumption of the confounding substance, and the first TH_(ROI) reach the threshold; the computer does not detect the physiological response based on second TH_(ROI) for which there is an indication indicating that the second TH_(ROI) were affected by a consumption of the confounding substance, and the second TH_(ROI) also reach the threshold; and the computer does not detect the physiological response based on third TH_(ROI) for which there is no indication indicating that the third TH_(ROI) were affected by a consumption the confounding substance, and the third TH_(ROI) do not reach the threshold.

The following three figures illustrate scenarios where issuing of alerts are dependent on the consumption of confounding substances. FIG. 54 illustrates that the effect of consuming alcohol on a certain TH_(ROI) usually decreases after duration typical to the user (e.g., the duration is based on previous measurements of the user). Thus, when the effect remains high there may be a problem and the system may issue an alert. The figure illustrates an outward-facing visible-light camera 525 that generates the indications indicative of when the user consumes alcoholic beverages.

FIG. 55 illustrates a usual increase in a certain TH_(ROI) while the user smokes. The system identifies when the user smoked (e.g., based on images taken by the outward-facing visible-light camera 525) and doesn't alert because of an increase in TH_(ROI) caused by the smoking. However, when the temperature rises without the user having smoked for a certain time, then it may be a sign that there is a problem, and the user might need to be alerted.

FIG. 56 illustrates the expected decrease in a certain TH_(ROI) after the user takes medication, based on previous TH_(ROI) of the user. The system identifies when the medication is consumed, and does not generate an alert at those times. However, when TH_(ROI) falls without medication having been taken, it may indicate a physiological response of which the user should be made aware.

The following method for detecting a physiological response while taking into account consumption of a confounding substance may be used, in some embodiments, by the system described above, which detects a physiological response while taking into account a consumption of a confounding substance. The steps described below may be performed by running a computer program having instructions for implementing the method. Optionally, the instructions may be stored on a computer-readable medium, which may optionally be a non-transitory computer-readable medium. In response to execution by a system including a processor and memory, the instructions cause the system to perform the following steps:

In Step 1, taking thermal measurements of an ROI (TH_(ROI)) on the user's face utilizing an inward-facing head-mounted thermal camera.

In Step 2, receiving an indication indicative of consuming a confounding substance that affects TH_(ROI). Optionally, the indication is received from one or more of the various device described above that provide an indication indicative of consuming a confounding substance. Optionally, the indication is generated based on image processing of images taken by a head-mounted visible-light camera having in its field of a volume that protrudes out of the user's mouth.

And in Step 3, detecting the physiological response, while the consumed confounding substance affects TH_(ROI), based on TH_(ROI), the indication, and a model. Optionally, the model was trained on: a first set of TH_(ROI) taken while the confounding substance affected TH_(ROI), and a second set of TH_(ROI) taken while the confounding substance did not affect TH_(ROI). Optionally, the model is a machine learning-based model, and this step involves: generating feature values based on TH_(ROI) and the indication, and utilizing the machine learning-based model to detect the physiological response based on the feature values.

One way in which a user may wear a head-mounted camera (such as CAM or VCAM) involves attaching a clip-on device that houses the camera onto a frame worn by the user, such as an eyeglasses frame. This may enable the user to be selective regarding when to use the head-mounted camera and take advantage of eyeglasses that he or she owns, which may be comfortable and/or esthetically pleasing.

In some embodiments, the clip-on device includes a body that may be attached and detached, multiple times, from a pair of eyeglasses in order to secure and release the clip-on device from the eyeglasses. The body is a structure that has one or more components fixed to it. For example, the body may have one or more inward-facing camera fixed to it. Additionally, the body may have a wireless communication module fixed to it. Some additional components that may each be optionally fixed to the body include a processor, a battery, and one or more outward-facing cameras.

In one example, “eyeglasses” are limited to prescription eyeglasses, prescription sunglasses, plano sunglasses, and/or augmented reality eyeglasses. This means that “eyeglasses” do not refer to helmets, hats, virtual reality devices, and goggles designed to be worn over eyeglasses. Additionally or alternatively, neither attaching the clip-on device to the eyeglasses nor detaching the clip-on device from the eyeglasses should take more than 10 seconds for an average user. This means that manipulating the clip-on device is not a complicated task. Optionally, the body is configured to be detached from the eyeglasses by the user who wears the eyeglasses, who is not a technician, and without using a tool such as a screwdriver or a knife. Thus, the clip-on device may be attached and detached as needed, e.g., enabling the user to attach the clip-on when there is a need to take measurements, and otherwise have it detached.

In order to be warn comfortably, possibly for long durations, the clip-on device is a lightweight device, weighing less than 40 g (i.e., the total weight of the body and the components fixed to it is less than 40 g). Optionally, the clip-on device weighs below 20 g and/or below 10 g.

The body is a structure to which components (e.g., an inward-facing camera) may be fixed such that the various components do not fall off while the clip-on device is attached to the eyeglasses. Optionally, at least some of the various components that are fixed to the body remain in the same location and/or orientation when the body is attached to the eyeglasses. Herein, stating that a component is “fixed” to the body is intended to indicate that, during normal use (e.g., involving securing/releasing the clip-on device), the components are typically not detached from the body. This is opposed to the body itself, which in normal use is separated from the eyeglasses frame, and as such, is not considered “fixed” to the eyeglasses frame.

In some embodiments, the body is a rigid structure made of a material such as plastic, metal, and/or an alloy (e.g., carbon alloy). Optionally, the rigid structure is shaped such that it fits the contours of at least a portion of the frame of the eyeglasses in order to enable a secure and stable attachment to the eyeglasses. In other embodiments, the body may be made of a flexible material, such as rubber. Optionally, the flexible body is shaped such that it fits the contours of at least a portion of the frame of the eyeglasses in order to enable a secure and stable attachment to the eyeglasses. Additionally or alternatively, the flexible body may assume the shape of a portion of the frame when it is attached to the eyeglasses.

The body may utilize various mechanisms in order to stay attached to the eyeglasses. In one embodiment, the body may include a clip member configured to being clipped on the eyeglasses. In another embodiment, the body may include a magnet configured to attach to a magnet connected to the eyeglasses and/or to a metallic portion of the eyeglasses. In yet another embodiment, the body may include a resting tab configured to secure the clip-on to the eyeglasses. In still another embodiment, the body may include a retention member (e.g., a clasp, buckle, clamp, fastener, hook, or latch) configured to impermanently couple the clip-on to the eyeglasses. For example, clasp 147 is utilized to secure the clip-on device illustrated in FIG. 17a to the frame of the eyeglasses. And in yet another embodiment, the body may include a spring configured to apply force that presses the body towards the eyeglasses. An example of this type of mechanism is illustrated in FIG. 19a where spring 175 is used to apply force that pushes body 170 and secures it in place to frame 176.

Herein, to “impermanently couple” something means to attach in a way that is easily detached without excessive effort. For example, coupling something by clipping it on or closing a latch is considered impermanently coupling it. Coupling by screwing a screw with a screwdriver, gluing, or welding is not considered impermanently coupling. The latter would be examples of what may be considered to “fix” a component to the body.

The inward-facing camera is fixed to the body. It takes images of a region of interest on the face of a user who wears the eyeglasses. Optionally, the inward-facing camera remains pointed at the region of interest even when the user's head makes lateral and/or angular movements. The inward-facing camera may be any of the CAMs and/or VCAMs described in this disclosure. Optionally, the inward-facing camera weighs less than 10 g, 5 g or 1 g. Optionally, the inward-facing camera is a thermal camera based on a thermopile sensor, a pyroelectric sensor, or a microbolometer sensor, which may be a FPA sensor.

In one embodiment, the inward-facing camera includes a multi-pixel sensor and a lens, and the sensor plane is tilted by more than 2° relative to the lens plane according to the Scheimpflug principle in order to capture sharper images when the body is attached to the eyeglasses that are worn by a user.

The clip-one device may include additional components that are fixed to it. In one embodiment, the clip-on device include a wireless communication module fixed to the body which transmits measurements (e.g., images and/or thermal measurements) taken by one or more of the cameras that are fixed to the body. Optionally, the clip-on device may include a battery fixed to the body, which provides power to one or more components fixed to the body. Optionally, the clip-on device may include a processor that controls the operation of one or more of the components fixed to the body and/or processes measurements taken by the camera fixed to the body.

In some embodiments, a computer receives measurements taken by the inward-facing camera (and possibly other cameras fixed to the body), and utilizes the measurements to detect a physiological response. Optionally, the computer is not fixed to the body. For example, the computer may belong to a device of the user (e.g., a smartphone or a smartwatch), or the computer may be a cloud-based server. Optionally, the computer receives, over a wireless channel, the measurements, which are sent by the wireless communication module.

The following are various examples of embodiments using different types of inward- and outward-facing cameras that are fixed to the body, which may be used to take images of various regions of interest on the face of the user who wears the eyeglasses. It is to be noted that while the discussion below generally refers to a single “inward-facing camera” and/or a single “outward-facing camera”, embodiments of the clip-on device may include multiple inward- and/or outward-facing cameras.

In some embodiments, the inward-facing camera is a thermal camera. Optionally, when the body is attached to the eyeglasses, the thermal camera is located less than 5 cm from the user's face. Optionally, measurements taken by the thermal camera are transmitted by the wireless communication module and are received by a computer that uses them to detect a physiological response of the user. In one example, when the body is attached to the eyeglasses, the optical axis of the thermal camera is above 20° from the Frankfort horizontal plane, and the thermal camera takes thermal measurements of a region on the user's forehead. In another example, when the body is attached to the eyeglasses, the thermal camera takes thermal measurements of a region on the user's nose. In yet another example, when the body is attached to the eyeglasses, the thermal camera takes thermal measurements of a region on a periorbital area of the user.

In one embodiment, the inward-facing camera is a thermal camera. When the body is attached to the eyeglasses, the thermal camera is located below eye-level of a user who wears the eyeglasses and at least 2 cm from the vertical symmetry axis that divides the user's face (i.e., the axis the goes down the center of the user's forehead and nose). Additionally, when the body is attached to the eyeglasses, the inward-facing thermal camera takes thermal measurements of a region on at least one of the following parts of the user's face: upper lip, lips, and a cheek. Optionally, measurements taken by the thermal camera are transmitted by the wireless communication module and are received by a computer that uses them to detect a physiological response of the user.

In another embodiment, the inward-facing camera is a visible-light camera. Optionally, when the body is attached to the eyeglasses, the visible-light camera is located less than 10 cm from the user's face. Optionally, images taken by the visible-light camera are transmitted by the wireless communication module and are received by a computer that uses them to detect a physiological response of the user. Optionally, the computer detects the physiological response based on facial skin color changes (FSCC) that are recognizable in the images. In one example, when the body is attached to the eyeglasses, the optical axis of the visible-light camera is above 20° from the Frankfort horizontal plane, and the visible-light camera takes images of a region located above the user's eyes. In another example, when the body is attached to the eyeglasses, the visible-light camera takes images of a region on the nose of a user who wears the eyeglasses. In still another example, the computer detects the physiological response based on facial expressions, and when the body is attached to the eyeglasses, the visible-light camera takes images of a region above or below the user's eyes.

In still another embodiment, the inward-facing camera is a visible-light camera, and when the body is attached to the eyeglasses, the visible-light camera takes images of a region on an eye (IM_(E)) of a user who wears the eyeglasses, and is located less than 10 cm from the user's face. Optionally, the images are transmitted by the wireless communication module and are received by a computer that detects a physiological response based in IM_(E).

In one example, the computer detects the physiological response based on color changes to certain parts of the eye, such as the sclera and/or the iris. Due to the many blood vessels that are close to the surface of the eye, physiological responses that are manifested through changes to the blood flow (e.g., a cardiac pulse and certain emotional responses), may cause recognizable changes to the color of the certain parts of the eye. The various techniques described in this disclosure for detecting a physiological response based on FSCC that is recognizable in images can be applied by one skilled in the art to detect a physiological response based on color changes to the sclera and/or iris; while the sclera and iris are not the same color as a person's skin, they too exhibit blood flow-related color changes that are qualitatively similar to FSCC, and thus may be analyzed using similar techniques to the techniques used to analyze FSCC involving the forehead, nose, and/or cheeks.

In another example, IM_(E) may be utilized to determine the size of the pupil, which may be utilized by the computer to detect certain emotional responses (such as based on the assumption that the pupil's response reflects emotional arousal associated with increased sympathetic activity).

If needed as part of the computer's detection of the physiological response, identifying which portions of IM_(E) correspond to certain parts of the eye (e.g., the sclera or iris) can be done utilizing various image processing techniques known in the art. For example, identifying the iris and pupil size may be done using the techniques described in US patent application 20060147094, or in Hayes, Taylor R., and Alexander A. Petrov. “Mapping and correcting the influence of gaze position on pupil size measurements.” Behavior Research Methods 48.2 (2016): 510-527. Additionally, due to the distinct color differences between the skin, the iris, and the sclera, identification of the iris and/or the white sclera can be easily done by image processing methods known in the art.

In one embodiment, the inward-facing camera is a visible-light camera; when the body is attached to the eyeglasses, the visible-light camera is located below eye-level of a user who wears the eyeglasses, and at least 2 cm from the vertical symmetry axis that divides the user's face. The visible-light camera takes images (IM_(ROI)) of a region on the upper lip, lips, and/or a cheek. Optionally, IM_(ROI) are transmitted by the wireless communication module and are received by a computer that uses them to detect a physiological response. In one example, the physiological response is an emotional response, which is detected based on extracting facial expressions from IM_(ROI). In another example, the physiological response is an emotional response, which is detected based on FSCC recognizable in IM_(ROI). In still another example, the physiological response, which is detected based FSCC recognizable in IM_(ROI), is heart rate and/or breathing rate.

The body may include an outward-facing camera that may be utilized to provide measurements that may be used to account for various environmental interferences that can decrease detections of the physiological response of a user who wears the eyeglasses. Optionally, the outward-facing camera is a head-mounted camera. Optionally, the outward-facing camera is fixed to the body.

In one embodiment, the inward-facing camera is a thermal camera, and when the body is attached to the eyeglasses, the thermal camera is located less than 10 cm from the face of the user who wears the eyeglasses, and takes thermal measurements of a region of interest (TH_(ROI)) on the face of the user. In this embodiment, an outward-facing head-mounted thermal camera takes thermal measurements of the environment (TH_(ENV)). The wireless communication module transmits TH_(ROI) and TH_(ENV) to a computer that detects a physiological response of the user based on TH_(ROI) and TH_(ENV). Optionally, the computer utilizes TH_(ENV) to account for thermal interferences from the environment, as discussed elsewhere herein.

In another embodiment, the inward-facing camera is a visible-light camera, and when the body is attached to the eyeglasses, the visible-light camera is located less than 10 cm from the face of the user who wears the eyeglasses and takes images of a region of interest (IM_(ROI)) on the face of the user. In this embodiment, an outward-facing head-mounted visible-light camera takes images of the environment (IM_(EN)). The wireless communication module transmits IM_(ROI) and IM_(ENV) to a computer that detects a physiological response of the user based on IM_(ROI) and IM_(ENV). Optionally, the computer detects the physiological response based on FSCC recognizable in IM_(ROI), and utilizes IM_(ENV) to account for variations in ambient light, as discussed elsewhere herein.

Inward-facing cameras attached to the body may be utilized for additional purposes, beyond detection of physiological responses. In one embodiment, the inward-facing camera is a visible-light camera, and the clip-on device includes a second visible-light camera that is also fixed to the body. Optionally, the visible-light camera and/or the second visible-light camera are light field cameras. Optionally, when the body is attached to the eyeglasses, the first and second visible-light cameras are located less than 10 cm from the user's face, and take images of a first region above eye-level and a second region on the upper lip (IM_(ROI) and IM_(ROI2), respectively). Optionally, the wireless communication module transmits IM_(ROI) and IM_(ROI2) to a computer that generates an avatar of the user based on IM_(ROI) and IM_(ROI2). Some of the various approaches that may be utilized to generate the avatar based on IM_(ROI) and IM_(ROI2) are described in co-pending US patent publication 2016/0360970.

Different embodiments of the clip-on device may involve devices of various shapes, sizes, and/or locations of attachment to the eyeglasses. FIG. 16a to FIG. 20 illustrate some examples of clip-on devices. When the body is attached to the eyeglasses, most of the clip-on device may be located in front of the frame of the eyeglasses, as illustrated in FIG. 16b , FIG. 17b , and FIG. 20, or alternatively, most of the clip-on device may be located behind the frame, as illustrated in FIG. 18b and FIG. 19b . Some clip-on devices may include a single unit, such as illustrated in FIG. 17a and FIG. 19a . While other clip-on devices may include multiple units (which each may optionally be considered a separate clip-on device). Examples of multiple units being attached to the frame are illustrated in FIG. 16b , FIG. 18b , and FIG. 20. The following is a more detailed discussion regarding embodiments illustrated in the figures mentioned above.

FIG. 16a , FIG. 16b , and FIG. 16c illustrate two right and left clip-on devices comprising bodies 141 and 142, respectively, which are configured to attached/detached from an eyeglasses frame 140. The body 142 has multiple inward-facing cameras fixed to it, such as camera 143 that points at a region on the lower part of the face (such as the upper lip, mouth, nose, and/or cheek), and camera 144 that points at the forehead. The body 142 may include other electronics 145, such as a processor, a battery, and/or a wireless communication module. The bodies 141 and 142 of the left and right clip-on devices may include additional cameras illustrated in the drawings as black circles.

In one another embodiment, the eyeglasses include left and right lenses, and when the body is attached to the eyeglasses, most of the volume of the clip-on device is located to the left of the left lens or to the right of the right lens. Optionally, the inward-facing camera takes images of at least one of: a region on the nose of a user wearing the eyeglasses, and a region on the mouth of the user. Optionally, a portion of the clip-on device that is located to the left of the left lens or to the right of the right lens does not obstruct the sight of the user when looking forward.

FIG. 17a and FIG. 17b illustrate a clip-on device that includes a body 150, to which two head-mounted cameras are fixed: a head-mounted camera 148 that points at a region on the lower part of the face (such as the nose), and a head-mounted camera 149 that points at the forehead. The other electronics (such as a processor, a battery, and/or a wireless communication module) are located inside the body 150. The clip-on device is attached and detached from the frame of the eyeglasses with the clasp 147.

In one embodiment, when the body is attached to the eyeglasses, most of the volume of the clip-on device is located above the lenses of the eyeglasses, and the inward-facing camera takes images of a region on the forehead of a user who wears the eyeglasses. Optionally, a portion of the clip-on device that is located above the lenses of the eyeglasses does not obstruct the sight of the user when looking forward.

While the clip-on device may often have a design intended to reduce the extent to which it sticks out beyond the frame, in some embodiments, the clip-on device may include various protruding arms. Optionally, these arms may be utilized in order to position one or more cameras in a position suitable for taking images of certain regions of the face. FIG. 20 illustrates right and left clip-on devices that include bodies 153 and 154, respectively, which are configured to attached/detached from an eyeglasses frame. These bodies have protruding arms that hold the head-mounted cameras. Head-mounted camera 155 measures a region on the lower part of the face, head-mounted camera 156 measures regions on the forehead. The left clip-on device also includes other electronics 157 (such as a processor, a battery, and/or a wireless communication module). The clip-on devices illustrated in this figure may include additional cameras illustrated in the drawings as black circles.

In other embodiments, at least a certain portion of the clip-on device is located behind the eyeglasses' frame. Thus, when the clip-on device is attached to the eyeglasses, they may remain aesthetically pleasing, and attaching the clip-on device may cause little or no blocking of the user's vision. FIG. 18b and FIG. 19b illustrate two examples of clip-on devices that are mostly attached behind the frame. The following are some additional examples of embodiments in which a portion of the clip-on device may be located behind the frame.

FIG. 18a and FIG. 18b illustrate two, right and left, clip-on devices with bodies 160 and 161, respectively, configured to be attached behind an eyeglasses frame 165. The body 160 has various components fixed to it which include: an inward-facing head-mounted camera 162 pointed at a region below eye-level (such as the upper lip, mouth, nose, and/or cheek), an inward-facing head-mounted camera 163 pointed at a region above eye-level (such as the forehead), and other electronics 164 (such as a processor, a battery, and/or a wireless communication module). The right and left clip-on devices may include additional cameras illustrated in the drawings as black circles.

FIG. 19a and FIG. 19b illustrate a single-unit clip-on device that includes the body 170, which is configured to be attached behind the eyeglasses frame 176. The body 170 has various cameras fixed to it, such as head-mounted cameras 171 and 172 that are pointed at regions on the lower part of the face (such as the upper lip, mouth, nose, and/or cheek), and head-mounted cameras 173 and 174 that are pointed at the forehead. The spring 175 is configured to apply force that holds the body 170 to the frame 176. Other electronics 177 (such as a processor, a battery, and/or a wireless communication module), may also be fixed to the body 170. The clip-on device may include additional cameras illustrated in the drawings as black circles.

In one embodiment, when the body is attached to the eyeglasses, more than 50% of the out-facing surface of the clip-on device is located behind the eyeglasses frame. Optionally, a portion of the clip-on device that is located behind the eyeglasses frame is occluded from a viewer positioned directly opposite to the eyeglasses, at the same height as the eyeglasses. Thus, a portion of the clip-on device that is behind the frame might not be visible to other people from many angles, which can make the clip-on device less conspicuous and/or more aesthetically pleasing. Optionally, a larger portion of the clip-on device is behind the frame when the body is attached to the eyeglasses, such as more than 75% or 90% of the out-facing surface.

Various physiological responses may be detected based on Facial skin color changes (FSCC) that occur on a user's face. In one embodiment, a system configured to detect a physiological response based on FSCC includes at least an inward-facing head-mounted visible-light camera (VCAM_(in)) and a computer. The system may optionally include additional elements such as a frame and additional inward-facing camera(s) and/or outward-facing camera(s).

FIG. 47 illustrates one embodiment of the system configured to detect a physiological response based on FSCC. The system includes a frame 735 (e.g., an eyeglasses frame) to which various cameras are physically coupled. These cameras include visible-light cameras 740, 741, 742, and 743, which may each take images of regions on the user's cheeks and/or nose. Each of these cameras may possibly be VCAM_(in), which is discussed in more detail below. Another possibility for VCAM_(in) is camera 745 that takes images of a region on the user's forehead and is coupled to the upper portion of the frame. Visible-light camera 737, which takes images of the environment (IM_(ENV)), is an example of VCAM_(out) discussed below, which may optionally be included in some embodiments. Additional cameras that may optionally be included in some embodiments are outward-facing thermal camera 738 (which may be used to take TH_(ENV) mentioned below) and inward-facing thermal camera 739 (which may be used to take TH_(ROI2) mentioned below).

VCAM_(in) is worn on the user's head and takes images of a region of interest (IM_(ROI)) on the user's face. Depending on the physiological response being detected, the ROI may cover various regions on the user's face. In one example, the ROI is on a cheek of the user, a region on the user's nose, and/or a region on the user's forehead. Optionally, VCAM_(in) does not occlude the ROI, is located less than 10 cm from the user's face, and weighs below 10 g. The ROI is illuminated by ambient light. Optionally, the system does not occlude the ROI, and the ROI is not illuminated by a head-mounted light source. Alternatively, the ROI may be illuminated by a head-mounted light source that is weaker than the ambient light.

The computer detects the physiological response based on IM_(ROI) by relying on effects of FSCC that are recognizable in IM_(ROI). Herein, sentences of the form “FSCC recognizable in IM_(ROI)” refer to effects of FSCC that may be identified and/or utilized by the computer, which are usually not recognized by the naked eye. The FSCC phenomenon may be utilized to detect various types of physiological responses. In one embodiment, the physiological response that is detected may involve an expression of emotional response of the user. For example, the computer may detect whether the user's emotional response is neutral, positive, or negative. In another example, the computer may detect an emotional response that falls into a more specific category such as distress, happiness, anxiousness, sadness, frustration, intrigue, joy, disgust, anger, etc. Optionally, the expression of the emotional response may involve the user making a facial expression and/or a microexpression (whose occurrence may optionally be detected based on IM_(ROI)). In another embodiment, detecting the physiological response involves determining one or more physiological signals of the user, such as a heart rate (which may also be referred to as “cardiac pulse”), heart rate variability, and/or a breathing rate.

IM_(ROI) are images generated based on ambient light illumination that is reflected from the user's face. Variations in the reflected ambient light may cause FSCC that are unrelated to the physiological response being detected, and thus possibly lead to errors in the detection of the physiological response. In some embodiments, the system includes an outward-facing head-mounted visible-light camera (VCAM_(out)), which is worn on the user's head, and takes images of the environment (IM_(ENV)). Optionally, VCAM_(out) is located less than 10 cm from the user's face and weighs below 10 g. Optionally, VCAM_(out) may include optics that provide it with a wide field of view. Optionally, the computer detects the physiological response based on both IM_(ROI) and IM_(ENV). Given that IM_(ENV) is indicative of illumination towards the face and IM_(ROI) is indicative of reflections from the face, utilizing IM_(ENV) in the detection of the physiological response can account, at least in part, for variations in ambient light that, when left unaccounted, may possibly lead to errors in detection of the physiological response.

It is noted that the system may include multiple VCAM_(in) configured to take images of various ROIs on the face, IM_(ROI) may include images taken from the multiple VCAM_(in) and multiple VCAM_(out) located at different locations and/or orientation relative to the face may be used to take images of the environment.

In some embodiments, VCAM_(in) and/or VCAM_(out) are physically coupled to a frame, such as an eyeglasses frame or an augmented realty device frame. Optionally, the angle between the optical axes of VCAM_(in) and VCAM_(out) is known to the computer, and may be utilized in the detection of the physiological response. Optionally, the angle between the optical axes of VCAM_(in) and VCAM_(out) is fixed.

Due to the proximity of VCAM_(in) to the face, in some embodiments, there may be an acute angle between the optical axis of VCAM_(in) and the ROI (e.g., when the ROI includes a region on the forehead). In order to improve the sharpness of IM_(ROI), VCAM_(in) may be configured to operate in a way that takes advantage of the Scheimpflug principle. In one embodiment, VCAM_(in) includes a sensor and a lens; the sensor plane is tilted by a fixed angle greater than 2° relative to the lens plane according to the Scheimpflug principle in order to capture a sharper image when VCAM_(in) is worn by the user (where the lens plane refers to a plane that is perpendicular to the optical axis of the lens, which may include one or more lenses). Optionally, VCAM_(in) does not occlude the ROI. In another embodiment, VCAM_(in) includes a sensor, a lens, and a motor; the motor tilts the lens relative to the sensor according to the Scheimpflug principle. The tilt improves the sharpness of IM_(ROI) when VCAM_(in) is worn by the user.

In addition to capturing images in the visible spectrum, some embodiments may involve capturing light in the near infrared spectrum (NIR). In some embodiments, VCAM_(in) and/or VCAM_(out) may include optics and sensors that capture light rays in at least one of the following NIR spectrum intervals: 700-800 nm, 700-900 nm, 700-1,000 nm. Optionally, the computer may utilize data obtained in a NIR spectrum interval to detect the physiological response (in addition to or instead of data obtained from the visible spectrum). Optionally, the sensors may be CCD sensors designed to be sensitive in the NIR spectrum and/or CMOS sensors designed to be sensitive in the NIR spectrum.

One advantage of having VCAM_(in) coupled to the frame involves the handling of chromatic aberrations. Chromatic aberrations refract different wavelengths of light at different angles, depending on the incident angle. When VCAM_(in) is physically coupled to the frame, the angle between VCAM_(in) and the ROI is known, and thus the computer may be able to select certain subsets of pixels, which are expected to measure light of certain wavelengths from the ROI. In one embodiment, VCAM_(in) includes a lens and a sensor comprising pixels; the lens generates chromatic aberrations that refract red and blue light rays in different angles; the computer selects, based on the angle between the camera and the ROI (when the user wears the frame), a first subset of pixels to measure the blue light rays reflected from the ROI, and a second subset of pixels to measure the red light rays reflected from the ROI. Optionally, the first and second subsets are not the same. Optionally, VCAM_(in) may include a sensor that captures light rays also in a portion of the NIR spectrum, and the computer selects, based on the angle between VCAM_(in) and the ROI, a third subset of pixels to measure the NIR light rays reflected from the ROI. Optionally, the second and third subsets are not the same.

The computer may utilize various approaches in order to detect the physiological response based on IM_(ROI). Some examples of how such a detection may be implemented are provided in the prior art references mentioned above, which rely on FSCC to detect the physiological response. It is to be noted that while the prior art approaches involve analysis of video obtained from cameras that are not head-mounted, are typically more distant from the ROI than VCAM_(in), and are possibly at different orientations relative to the ROI, the computational approaches described in the prior art used to detect physiological responses can be readily adapted by one skilled in the art to handle IM_(ROI). In some cases, embodiments described herein may provide video in which a desired signal is more easily detectable compared to some of the prior art approaches. For example, given the short distance from VCAM_(in) to the ROI, the ROI is expected to cover a larger portion of the images in IM_(ROI) compared to images obtained by video cameras in some of the prior art references. Additionally, due to the proximity of VCAM_(in) to the ROI, additional illumination that is required in some prior art approaches, such as illuminating the skin for a pulse oximeter to obtain a photoplethysmographic (PPG) signal, may not be needed. Furthermore, given VCAM_(in)'s fixed location and orientation relative to the ROI (even when the user makes lateral and/or angular movements), many pre-processing steps that need to be implemented by the prior art approaches, such as image registration and/or face tracking, are extremely simplified in embodiments described herein, or may be foregone altogether.

IM_(ROI) may undergo various preprocessing steps prior to being used by the computer to detect the physiological response and/or as part of the process of the detection of the physiological response. Some non-limiting examples of the preprocessing include: normalization of pixel intensities (e.g., to obtain a zero-mean unit variance time series signal), and conditioning a time series signal by constructing a square wave, a sine wave, or a user defined shape, such as that obtained from an ECG signal or a PPG signal as described in U.S. Pat. No. 8,617,081. Additionally or alternatively, some embodiments may involve generating feature values based on a single image or a sequence of images. In some examples, generation of feature values from one or more images may involve utilization of some of the various approaches described in this disclosure for generation of high-level and/or low-level image-based features.

The following is a discussion of some approaches that may be utilized by the computer to detect the physiological response based on IM_(ROI). Additionally, implementation-related details may be found in the provided references and the references cited therein. Optionally, IM_(ENV) may also be utilized by the computer to detect the physiological response (in addition to IM_(ROI)), as explained in more detail below.

In some embodiments, the physiological response may be detected using signal processing and/or analytical approaches. Optionally, these approaches may be used for detecting repetitive physiological signals (e.g., a heart rate, heart rate variability, or a breathing rate) in IM_(ROI) taken during a certain period. Optionally, the detected physiological response represents the value of the physiological signal of the user during the certain period.

In one example, U.S. Pat. No. 8,768,438, titled “Determining cardiac arrhythmia from a video of a subject being monitored for cardiac function”, describes how a heart rate may be determined based on FSCC, which are represented in a PPG signal obtained from video of the user. In this example, a time series signal is generated from video images of a subject's exposed skin, and a reference signal is used to perform a constrained source separation (which is a variant of ICA) on the time series signals to obtain the PPG signal. Peak-to-peak pulse points are detected in the PPG signal, which may be analyzed to determine parameters such as heart rate, heart rate variability, and/or to obtain peak-to-peak pulse dynamics that can be indicative of conditions such as cardiac arrhythmia.

In another example, U.S. Pat. No. 8,977,347, titled “Video-based estimation of heart rate variability”, describes how a times-series signal similar to the one described above may be subjected to a different type of analysis to detect the heart rate variability. In this example, the time series data are de-trended to remove slow non-stationary trends from the signal and filtered (e.g., using bandpass filtering). Following that, low frequency and high frequency components of the integrated power spectrum within the time series signal are extracted using Fast Fourier Transform (FFT). A ratio of the low and high frequency of the integrated power spectrum within these components is computed. And analysis of the dynamics of this ratio over time is used to estimate heart rate variability.

In yet another example, U.S. Pat. No. 9,020,185, titled “Systems and methods for non-contact heart rate sensing”, describes how a times-series signals obtained from video of a user can be filtered and processed to separate an underlying pulsing signal by, for example, using an ICA algorithm. The separated pulsing signal from the algorithm can be transformed into frequency spacing data using FFT, in which the heart rate can be extracted or estimated.

In some embodiments, the physiological response may be detected using machine learning-based methods. Optionally, these approaches may be used for detecting expressions of emotions and/or values of physiological signals.

Generally, machine learning-based approaches involve training a model on samples, with each sample including: feature values generated based on IM_(ROI) taken during a certain period, and a label indicative of the physiological response during the certain period. Optionally, the model may be personalized for a user by training the model on samples including: feature values generated based on IM_(ROI) of the user, and corresponding labels indicative of the user's respective physiological responses. Some of the feature values in a sample may be generated based on other sources of data (besides IM_(ROI)), such as measurements of the user generated using thermal cameras, movement sensors, and/or other physiological sensors, and/or measurements of the environment. Optionally, IM_(ROI) of the user taken during an earlier period may serve as a baseline to which to compare. Optionally, some of the feature values may include indications of confounding factors, which may affect FSCC, but are unrelated to the physiological response being detected. Some examples of confounding factors include touching the face, thermal radiation directed at the face, and consuming certain substances such as a medication, alcohol, caffeine, or nicotine.

Training the model may involve utilization of various training algorithms known in the art (e.g., algorithms for training neural networks and/or other approaches described herein). After the model is trained, feature values may be generated for IM_(ROI) for which the label (physiological response) is unknown, and the computer can utilize the model to detect the physiological response based on these feature values.

It is to be noted that in some embodiments, the model is trained based on data that includes measurements of the user, in which case it may be considered a personalized model of the user. In other embodiments, the model is trained based on data that includes measurements of one or more other users, in which case it may be considered a general model.

In order to achieve a robust model, which may be useful for detecting the physiological response in various conditions, in some embodiments, the samples used in the training may include samples based on IM_(ROI) taken in different conditions and include samples with various labels (e.g., expressing or not expressing certain emotions, or different values of physiological signals). Optionally, the samples are generated based on IM_(ROI) taken on different days.

The following are four examples of different compositions of samples that may be used when training the model in different embodiments. The “measured user” in the four examples below may be “the user” who is mentioned above (e.g., when the model is a personalized model that was trained on data that includes measurements of the user), or a user from among one or more other users (e.g., when the model is a general model that was trained on data that includes measurements of the other users). In a first example, the system does not occlude the ROI, and the model is trained on samples generated from a first set of IM_(ROI) taken while the measured user was indoors and not in direct sunlight, and is also trained on other samples generated from a second set of IM_(ROI) taken while the measured user was outdoors, in direct sunlight. In a second example, the model is trained on samples generated from a first set of IM_(ROI) taken during daytime, and is also trained on other samples generated from a second set of IM_(ROI) taken during nighttime. In a third example, the model is trained on samples generated from a first set of IM_(ROI) taken while the measured user was exercising and moving, and is also trained on other samples generated from a second set of IM_(ROI) taken while the measured user was sitting and not exercising. And a fourth example, the model is trained on samples generated from a first set of IM_(ROI) taken less than 30 minutes after the measured user had an alcoholic beverage, and is also trained on other samples generated from a second set of IM_(ROI) taken on a day in which the measured user did not have an alcoholic beverage.

Labels for the samples may be obtained from various sources. In one embodiment, the labels may be obtained utilizing one or more sensors that are not VCAM_(in). In one example, a heart rate and/or heart rate variability may be measured using an ECG sensor. In another example, the breathing rate may be determined using a smart shirt with sensors attached to the chest (e.g., a smart shirt by Hexoskin®). In yet another example, a type emotional response of the user may be determined based on analysis of a facial expression made by the user, analysis of the user's voice, analysis of thermal measurements of regions of the face of the user, and/or analysis of one or more of the following sensor-measured physiological signals of the user: a heart rate, heart rate variability, breathing rate, and galvanic skin response.

In another embodiment, a label describing an emotional response of the user may be inferred. In one example, the label may be based on semantic analysis of a communication of the user, which is indicative of the user's emotional state at the time IM_(ROI) were taken. In another example, the label may be generated in a process in which the user is exposed to certain content, and a label is determined based on an expected emotional response corresponding to the certain content (e.g., happiness is an expected response to a nice image while distress is an expected response to a disturbing image).

Due to the nature of the physiological responses being detected and the type of data (video images), a machine learning approach that may be applied in some embodiments is “deep learning”. In one embodiment, the model may include parameters describing multiple hidden layers of a neural network. Optionally, the model may include a convolution neural network (CNN). In one example, the CNN may be utilized to identify certain patterns in the video images, such as the patterns of the reflected FSCC due to the physiological response. Optionally, detecting the physiological response may be done based on multiple, possibly successive, images that display a certain pattern of change over time (i.e., across multiple frames), which characterizes the physiological response being detected. Thus, detecting the physiological response may involve retaining state information that is based on previous images. Optionally, the model may include parameters that describe an architecture that supports such a capability. In one example, the model may include parameters of a recurrent neural network (RNN), which is a connectionist model that captures the dynamics of sequences of samples via cycles in the network's nodes. This enables RNNs to retain a state that can represent information from an arbitrarily long context window. In one example, the RNN may be implemented using a long short-term memory (LSTM) architecture. In another example, the RNN may be implemented using a bidirectional recurrent neural network architecture (BRNN).

Some of the prior art references mentioned herein provide additional detailed examples of machine learning-based approaches that may be utilized to detect the physiological response (especially in the case in which it corresponds to an emotional response). In one example, Ramirez, et al. (“Color analysis of facial skin: Detection of emotional state”) describe detection of an emotional state using various machine learning algorithms including decision trees, multinomial logistic regression, and latent-dynamic conditional random fields. In another example, Wang, et al. (“Micro-expression recognition using color spaces”) describe various feature extraction methods and pixel color value transformations, which are used to generate inputs for a support vector machine (SVM) classifier trained to identify microexpressions.

As mentioned above, in some embodiments, IM_(ENV) may be utilized in the detection of the physiological response to account, at least in part, for illumination interferences that may lead to errors in the detection of the physiological response. There are different ways in which IM_(ENV) may be utilized for this purpose.

In one embodiment, when variations in IM_(ENV) reach a certain threshold (e.g., which may correspond to ambient light variations above a certain extent), the computer may refrain from detecting the physiological response.

In another embodiment, IM_(ENV) may be utilized to normalize IM_(ROI) with respect to the ambient light. For example, the intensity of pixels in IM_(ROI) may be adjusted based on the intensity of pixels in IM_(ENV) when IM_(ROI) were taken. US patent application number 20130215244 describes a method of normalization in which values of pixels from a region that does not contain a signal (e.g., background regions that include a different body part of the user or an object behind the user) are subtracted from regions of the image that contain the signal of the physiological response. While the computational approach described therein may be applied to embodiments in this disclosure, the exact setup described therein may not work well in some cases due to the close proximity of VCAM_(in) to the face and the fact that VCAM_(in) is head-mounted. Thus, it may be advantageous to subtract a signal from the environment (IM_(ENV)) that is obtained from VCAM_(out), which may more accurately represent the ambient light illuminating the face.

It is to be noted that training data that includes a ground-truth signal (i.e., values of the true physiological response corresponding to IM_(ROI) and IM_(ENV)) may be utilized to optimize the normalization procedure used to correct IM_(ROI) with respect to the ambient light measured in IM_(ENV). For example, such optimization may be used to determine parameter values of a function that performs the subtraction above, which lead to the most accurate detections of the physiological response.

In still another embodiment, IM_(ENV) may be utilized to generate feature values in addition to IM_(ROI). Optionally, at least some of the same types of feature values generated based on IM_(ROI) may also be generated based on IM_(ENV). Optionally, at least some of the feature values generated based on IM_(ENV) may relate to portions of images, such as average intensity of patches of pixels in IM_(ENV).

By utilizing IM_(ENV) as inputs used for the detection of the physiological response, a machine learning-based model may be trained to be robust, and less susceptible, to environmental interferences such as ambient light variations. For example, if the training data used to train the model includes samples in which no physiological response was present (e.g., no measured emotional response or microexpression was made), but some ambient light variations might have introduced some FSCC-related signal, the model will be trained such that feature values based on IM_(ENV) are used to account for such cases. This can enable the computer to negate, at least in part, the effects of such environmental interferences, and possibly make more accurate detections of the physiological response.

In one embodiment, the computer receives an indication indicative of the user consuming a confounding substance that is expected to affect FSCC (e.g., alcohol, drugs, certain medications, and/or cigarettes). The computer detects the physiological response, while the consumed confounding substance affects FSCC, based on: IM_(ROI), the indication, and a model that was trained on: a first set of IM_(ROI) taken while the confounding substance affected FSCC, and a second set of IM_(ROI) taken while the confounding substance did not affect FSCC.

Prior art FSCC systems are sensitive to user movements and do not operate well while the user is running. This is because state-of-the-art FSCC systems use hardware and automatic image trackers that are not accurate enough to crop correctly the ROI from the entire image while running, and the large errors in cropping the ROI are detrimental to the performances of the FSCC algorithms. Contrary to the prior art FSCC systems, the disclosed VCAM_(in) remains pointed at its ROI also when the user's head makes angular and lateral movements, and thus the complicated challenges related to image registration and ROI tracking are much simplified or even eliminated. Therefore, systems based on VCAM_(in) (such as the one illustrated in FIG. 47) may detect the physiological response (based on FSCC) also while the user is running.

VCAM_(in) may be pointed at different regions on the face. In a first embodiment, the ROI is on the forehead, VCAM_(in) is located less than 10 cm from the user's face, and optionally the optical axis of VCAM_(in) is above 20° from the Frankfort horizontal plane. In a second embodiment, the ROI is on the nose, and VCAM_(in) is located less than 10 cm from the user's face. Because VCAM_(in) is located close to the face, it is possible to calculate the FSCC based on a small ROI, which is irrelevant to the non-head-mounted prior arts that are limited by the accuracy of their automatic image tracker. In a third embodiment, VCAM_(in) is pointed at an eye of the user. The computer selects the sclera as the ROI and detects the physiological response based on color changes recognizable in IM_(ROI) of the sclera. In a fourth embodiment, VCAM_(in) is pointed at an eye of the user. The computer selects the iris as the ROI and detects the physiological response based on color changes recognizable in IM_(ROI) of the iris. Optionally, the computer further calculates changes to the pupil diameter based on the IM_(ROI) of the iris, and detects an emotional response of the user based on the changes to the pupil diameter.

In order to improve the detection accuracy, and in some cases in order to better account for interferences, the computer may utilize measurements of one or more head-mounted thermal cameras in the detection of the physiological response. In one embodiment, the system may include an inward-facing head-mounted thermal camera that takes thermal measurements of a second ROI (TH_(ROI2)) on the user's face. Optionally, ROI and ROI₂ overlap, and the computer utilizes TH_(ROI2) to detect the physiological response. Optionally, on average, detecting the physiological response based on both FSCC recognizable in IM_(ROI) and TH_(ROI2) is more accurate than detecting the physiological response based on the FSCC without TH_(ROI2). Optionally, the computer utilizes TH_(ROI2) to account, at least in part, for temperature changes, which may occur due to physical activity and/or consumption of certain medications that affect the blood flow. Optionally, the computer utilizes TH_(ROI2) by generating feature values based on TH_(ROI2), and utilizing a model that was trained on data comprising TH_(ROI2) in order to detect the physiological response.

In another embodiment, the system may include an outward-facing head-mounted thermal camera that takes thermal measurements of the environment (TH_(ENV)). Optionally, the computer may utilize TH_(ENV) to detect the physiological response (e.g., by generating feature values based on TH_(ENV) and utilizing a model trained on data comprising TH_(ENV)). Optionally, on average, detecting the physiological response based on both FSCC recognizable in IM_(ROI) and TH_(ENV) is more accurate than detecting the physiological response based on the FSCC without TH_(ENV). Optionally, the computer utilizes TH_(ENV) to account, at least in part, for thermal interferences from the environment, such as direct sunlight and/or a nearby heater.

In addition to detecting a physiological response, in some embodiments, the computer may utilize IM_(ROI) to generate an avatar of the user (e.g., in order to represent the user in a virtual environment). Optionally, the avatar may express emotional responses of the user, which are detected based on IM_(ROI). Optionally, the computer may modify the avatar of the user to show synthesized facial expressions that are not manifested in the user's actual facial expressions. In one embodiment, the synthesized facial expressions correspond to emotional responses detected based on FSCC that are recognizable in IM_(ROI). In another embodiment, the synthesized facial expressions correspond to emotional responses detected based on thermal measurements taken by CAM. Some of the various approaches that may be utilized to generate the avatar based on IM_(ROI) are described in co-pending US patent publication 2016/0360970.

The following method for detecting a physiological response based on facial skin color changes (FSCC) may be used by systems modeled according to FIG. 47. The steps described below may be performed by running a computer program having instructions for implementing the method. Optionally, the instructions may be stored on a computer-readable medium, which may optionally be a non-transitory computer-readable medium. In response to execution by a system including a processor and memory, the instructions cause the system to perform the following steps:

In Step 1, taking images of a region of interest (IM_(ROI)) on a user's face utilizing an inward-facing head-mounted visible-light camera (VCAM_(in)). The ROI is illuminated by ambient light.

And in Step 2, detecting the physiological response based on FSCC recognizable in IM_(ROI). Optionally, detecting the physiological response involves generating feature values based on IM_(ROI) and utilizing a model to calculate, based on the feature values, a value indicative of an extent of the physiological response. Optionally, the model was trained based on IM_(ROI) of the user taken during different days.

In one embodiment, the method may optionally include a step of taking images of the environment (IM_(ENV)) utilizing an outward-facing head-mounted visible-light camera (VCAM_(out)). Optionally, detecting the physiological response is also based on IM_(ENV).

Normally, the lens plane and the sensor plane of a camera are parallel, and the plane of focus (PoF) is parallel to the lens and sensor planes. If a planar object is also parallel to the sensor plane, it can coincide with the PoF, and the entire object can be captured sharply. If the lens plane is tilted (not parallel) relative to the sensor plane, it will be in focus along a line where it intersects the PoF. The Scheimpflug principle is a known geometric rule that describes the orientation of the plane of focus of a camera when the lens plane is tilted relative to the sensor plane.

FIG. 22a is a schematic illustration of an inward-facing head-mounted camera 550 embedded in an eyeglasses frame 551, which utilizes the Scheimpflug principle to improve the sharpness of the image taken by the camera 550. The camera 550 includes a sensor 558 and a lens 555. The tilt of the lens 555 relative to sensor 558, which may also be considered as the angle between the lens plane 555 and the sensor plane 559, is determined according to the expected position of the camera 550 relative to the ROI 552 when the user wears the eyeglasses. For a refractive optical lens, the “lens plane” 556 refers to a plane that is perpendicular to the optical axis of the lens 555. Herein, the singular also includes the plural, and the term “lens” refers to one or more lenses. When “lens” refers to multiple lenses (which is usually the case in most modern cameras having a lens module with multiple lenses), then the “lens plane” refers to a plane that is perpendicular to the optical axis of the lens module.

The Scheimpflug principle may be used for both thermal cameras (based on lenses and sensors for wavelengths longer than 2500 nm) and visible-light and/or near-IR cameras (based on lenses and sensors for wavelengths between 400-900 nm). FIG. 22b is a schematic illustration of a camera that is able to change the relative tilt between its lens and sensor planes according to the Scheimpflug principle. Housing 311 mounts a sensor 312 and lens 313. The lens 313 is tilted relative to the sensor 312. The tilt may be fixed according to the expected position of the camera relative to the ROI when the user wears the HMS, or may be adjusted using motor 314. The motor 314 may move the lens 313 and/or the sensor 312.

In one embodiment, an HMS device includes a frame configured to be worn on a user's head, and an inward-facing camera physically coupled to the frame. The inward-facing camera may assume one of two configurations: (i) the inward-facing camera is oriented such that the optical axis of the camera is above the Frankfort horizontal plane and pointed upward to capture an image of a region of interest (ROI) above the user's eyes, or (ii) the inward-facing camera is oriented such that the optical axis is below the Frankfort horizontal plane and pointed downward to capture an image of an ROI below the user's eyes. The inward-facing camera includes a sensor and a lens. The sensor plane is tilted by more than 2° relative to the lens plane according to the Scheimpflug principle in order to capture a sharper image.

In another embodiment, an HMS includes an inward-facing head-mounted camera that captures an image of an ROI on a user's face, when worn on the user's head. The ROI is on the user's forehead, nose, upper lip, cheek, and/or lips. The camera includes a sensor and a lens. And the sensor plane is tilted by more than 2° relative to the lens plane according to the Scheimpflug principle in order to capture a sharper image.

Because the face is not planar and the inward-facing head-mounted camera is located close to the face, an image captured by a camera having a wide field of view (FOV) and a low f-number may not be perfectly sharp, even after applying the Scheimpflug principle. Therefore, in some embodiments, the tilt between the lens plane and the sensor plane is selected such as to adjust the sharpness of the various areas covered in the ROI according to their importance for detecting the user's physiological response (which may be the user's emotional response in some cases). In one embodiment, the ROI covers first and second areas, where the first area includes finer details and/or is more important for detecting the physiological response than the second area. Therefore, the tilt between the lens and sensor planes is adjusted such that the image of the first area is shaper than the image of the second area.

In another embodiment, the ROI covers both a first area on the upper lip and a second area on a cheek, and the tilt is adjusted such that the image of the first area is shaper than the image of the second area, possibly because the upper lip usually provides more information and has more details relative to the cheek.

In still another embodiment, the ROI covers both a first area on the upper lip and a second area on the nose, and the tilt is adjusted such that the image of the first area is shaper than the image of the second area, possibly because the upper lip usually provides more information relative to the nose.

In still another embodiment, the ROI covers a first area on the cheek straight above the upper lip, a second area on the cheek from the edge of the upper lip towards the ear, and a third area on the nose. And the tilt between the lens plane and the sensor plane is adjusted such that the image of the first area is shaper than both the images of the second and third areas.

In still another embodiment, the ROI covers both a first area on the lips and a second area on the chin, and the tilt is adjusted such that the image of the first area is shaper than the image of the second area, possibly because the lips usually provides more information than the chin.

In still another embodiment, the camera is a visible-light camera, and the ROI covers both a first area on the lower forehead (including an eyebrow) and a second area on the upper forehead, and the tilt is adjusted such that the image of the first area is shaper than the image of the second area, possibly because the eyebrow provides more information about the user's emotional response than the upper forehead.

In still another embodiment, the camera is a thermal camera, and the ROI covers an area on the forehead, and the tilt is adjusted such that the image of a portion of the middle and upper part of the forehead (below the hair line) is shaper than the image of a portion of the lower part of the forehead, possibly because the middle and upper parts of the forehead are more indicative of prefrontal cortex activity than the lower part of the forehead, and movements of the eyebrows disturb the thermal measurements of the lower part of the forehead.

In one embodiment, the tilt between the lens plane and sensor plane is fixed. The fixed tilt is selected according to an expected orientation between the camera and the ROI when a user wears the frame. Having a fixed tilt between the lens and sensor planes may eliminate the need for an adjustable electromechanical tilting mechanism. As a result, a fixed tilt may reduce the weight and cost of the camera, while still providing a sharper image than an image that would be obtained from a similar camera in which the lens and sensor planes are parallel. The magnitude of the fixed tilt may be selected according to facial dimensions of an average user expected to wear the system, or according to a model of the specific user expected to wear the system in order to obtain the sharpest image.

In another embodiment, the system includes an adjustable electromechanical tilting mechanism configured to change the tilt between the lens and sensor planes according to the Scheimpflug principle based on the orientation between the camera and the ROI when the frame is worn by the user. The tilt may be achieved using at least one motor, such as a brushless DC motor, a stepper motor (without a feedback sensor), a brushed DC electric motor, a piezoelectric motor, and/or a micro-motion motor.

The adjustable electromechanical tilting mechanism configured to change the tilt between the lens and sensor planes may include one or more of the following mechanisms: (i) a mirror that changes its angle; (ii) a device that changes the angle of the lens relative to the sensor; and/or (iii) a device that changes the angle of the sensor relative to the lens. In one embodiment, the camera, including the adjustable electromechanical tilting mechanism, weighs less than 10 g, and the adjustable electromechanical tilting mechanism is able to change the tilt in a limited range below 30° between the two utmost orientations between the lens and sensor planes. Optionally, the adjustable electromechanical tilting mechanism is able to change the tilt in a limited range below 20° between the two utmost orientations between the lens and sensor planes. In another embodiment, the adjustable electromechanical tilting mechanism is able to change the tilt in a limited range below 10°. In some embodiments, being able to change the tilt in a limited range reduces at least one of the weight, cost, and size of the camera, which is advantageous for a wearable device. In one example, the camera is manufactured with a fixed predetermined tilt between the lens and sensor planes, which is in addition to the tilt provided by the adjustable electromechanical tilting mechanism. The fixed predetermined orientation may be determined according to the expected orientation between the camera and the ROI for an average user, such that the adjustable electromechanical tilting mechanism is used to fine-tune the tilt between the lens and sensor planes for the specific user who wears the frame and has facial dimensions that are different from the average user.

Various types of cameras may be utilized in different embodiments described herein. In one embodiment, the camera is a thermal camera that takes thermal measurements of the ROI with a focal plane array thermal sensor having an angle above 2° between the lens and sensor planes. Optionally, the thermal camera weighs below 10 g, is located less than 10 cm from the user's face, and the tilt of the lens plane relative to the sensor plane is fixed. The fixed tilt is selected according to an expected orientation between the camera and the ROI when the user wears the frame. Optionally, the system includes a computer to detect a physiological response based on the thermal measurements. Optionally, the computer processes time series measurements of each sensing element individually to detect the physiological response.

In another embodiment, the camera is a visible-light camera that takes visible-light images of the ROI, and a computer generates an avatar for the user based on the visible-light images. Some of the various approaches that may be utilized to generate the avatar based on the visible-light images are described in co-pending US patent publication 2016/0360970. Additionally or alternatively, the computer may detect an emotional response of the user based on (i) facial expressions in the visible-light images utilizing image processing, and/or (ii) facial skin color changes (FSCC), which result from concentration changes of hemoglobin and/or oxygenation.

It is to be noted that there are various approaches known in the art for identifying facial expressions from images. While many of these approaches were originally designed for full-face frontal images, those skilled in the art will recognize that algorithms designed for full-face frontal images may be easily adapted to be used with images obtained using the inward-facing head-mounted visible-light cameras disclosed herein. For example, the various machine learning techniques described in prior art references may be applied to feature values extracted from images that include portions of the face from orientations that are not directly in front of the user. Furthermore, due to the closeness of the visible-light cameras to the face, facial features are typically larger in images obtained by the systems described herein. Moreover, challenges such as image registration and face tracking are vastly simplified and possibly non-existent when using inward-facing head-mounted cameras. The reference Zeng, Zhihong, et al. “A survey of affect recognition methods: Audio, visual, and spontaneous expressions.” IEEE transactions on pattern analysis and machine intelligence 31.1 (2009): 39-58, describes some of the algorithmic approaches that may be used for this task. The following references discuss detection of emotional responses based on FSCC: (i) Ramirez, Geovany A., et al. “Color analysis of facial skin: Detection of emotional state” in Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition Workshops, 2014; and (ii) Wang, Su-Jing, et al. “Micro-expression recognition using color spaces”, in IEEE Transactions on Image Processing 24.12 (2015): 6034-6047.

In still another embodiment, the camera is a light field camera that implements a predetermined blurring at a certain Scheimpflug angle, and decodes the predetermined blurring as function of the certain Scheimpflug angle. The light field camera may include an autofocusing of the image obtained using the tilting mechanism based on the principle that scene points that are not in focus are blurred while scene points in focus are sharp. The autofocusing may study a small region around a given pixel; the region is expected to get sharper as the Scheimpflug adjustment gets better, and vice versa. Additionally or alternatively, the autofocusing may use the variance of the neighborhood around each pixel as a measure of sharpness, where a proper Scheimpflug adjustment should increase the variance.

Thermal and/or FSCC patterns corresponding to physiological responses may show high variability between different users due to variability of the their brains, blood vessel locations, skin properties, hair, physical conditions, and face shapes and sizes. Thus, patterns and/or various extractable features from one user's thermal and/or FSCC data may not be easily transferable to another user, or even to the same user under different physiological and/or mental conditions. Therefore, some of the embodiments described herein involve training personalized models involving thermal and/or FSCC patterns that are predictive of various user-defined categories of experiencing and/or perceiving certain events. Personalized models can overcome some of the possible disadvantages of using normed physiological statistics, which paves the way for personalized training, detection, and therapies, which are able to account for arbitrary user-defined physiological and/or mental states corresponding to a wide variety of individual needs. Leveraging machine learning algorithms can enable assignment of arbitrary user-defined physiological and/or mental states to recorded thermal and/or FSCC data during day-to-day activities, which are later used as basis for automatic detection and/or therapies for the user, optionally without involving a clinician.

The personalized model does not need to correspond to a standard universally applicable pattern, and thus the user may be free to define his/her arbitrary user-defined physiological and/or mental states. In other words, in addition to (or instead of) detecting a state that corresponds to some arbitrary population average, the personalized model allows a personalized detection of a user-defined state.

One embodiment in which a personalized model is utilized involves a training phase and an operation phase. In the training phase, the system identifies desired and/or undesired physiological and/or mental states of the user using active methods (e.g., the user presses a button) and/or passive methods (e.g., applying semantic analysis to the user's speech and typing). The system may also continue to update the personalized model to accommodate for changes over time, to supports increased efficacy, and to identify new personalized states beyond those represented by population average. Instead of relying on a model trained based on data obtained from a wide population, the personalized model may decouple commonly coupled ROIs and/or putative physiological responses from the applications, allowing the user to train the system to detect arbitrary personalized thermal and/or FSCC patterns that may not suite the wide population. Training the personalized model may be based on known machine learning methods such as neural networks, supervised machine learning, pattern recognition, pattern matching, etc. The system may detect, predict, and train for the arbitrary user-defined physiological and/or mental states, identified by personalized thermal and/or FSCC patterns, not limited to averages obtained from a wide population.

In the operation phase, the system alerts, predicts, and/or treats the user based on the personalized model. The system may alert when the user is in the desired/undesired state, predict when the user is going to be in that state, and treat the user to get into a desired state or avoid an undesired state by providing a feedback. The operation phase may include known biofeedback/neurofeedback interactive sessions tuned to guide the user towards the user-defined personalized physiological and/or mental states. For example, the personalized model may be trained to guide the user towards flow, creativity, curiosity, compassion, and/or happiness states, as defined and experienced by the user, and to alert against anger, aggression, boredom, and/or sadness, also as defined and experienced by the user, without these necessarily being suitable for the wide population.

One embodiment of a method for personalized thermal and/or FSCC detection includes a timestamping step, a machine learning step, a refinement step, an optional detection step, and an optional biofeedback step (where biofeedback refers also to neurofeedback).

In the timestamping step, an HMS records arbitrary user-defined physiological and/or mental states for personal use. The user may provide, via a user interface, timestamped markers on the recorded data used as labels by machine learning approaches for detecting target user-defined physiological and/or mental states (which may be desired or undesired states). When the user engages in a certain task, and as the user enters a target state, the user may (via a user interface) manual provide a timestamp to mark the time of entering into the target state, and/or the computer may set an automated timestamp based on inferring the entering into the target state from the user's performance and/or activities (for example, using predetermined limits of performance that once reached automatically trigger timestamping the recorded data as entering into the target state). Upon leaving the target state, the user may provide a timestamp to mark the leaving of the target state, and/or the computer may set an automated timestamp based on inferring the leaving of the target state from the user's performance and/or activities. Several iterations involving timestamping of entering and leaving the target state may complete the timestamping step.

In the machine learning step, the computer extracts and selects features from the thermal and/or FSCC measurements, labels the extracted and selected features according to the timestamps, and tries one or more machine learning algorithms to train a classifier, while treating the measurements as the training and testing sets. Optionally, for unique personalized states, the machine learning algorithm may be optimized for cross-validation by splitting the training set into a first part used for training and a second part used for testing. In addition, testing sets comprising data of other users may be used to measure the classifier's generality. The following examples illustrate various ways to label the HMS measurements based on the timestamps.

In a first example, the computer may (i) label as “not desired” TH_(ROI) taken before receiving from the user a first timestamp marking the entering into a desired state, (ii) label as “desired” TH_(ROI) taken after receiving the first timestamp and before receiving a second timestamp marking the leaving of the desired state, and (iii) label as “not desired” TH_(ROI) taken after receiving the second timestamp. Optionally, the computer may label as “unknown” TH_(ROI) taken sufficiently before receiving the first timestamp and TH_(ROI) taken sufficiently after receiving the second timestamp.

In a second example, the computer may (i) label as “leading to headache” TH_(ROI) taken during a first window of time before receiving from the user a first timestamp marking occurrence of a headache, (ii) label as “headache” TH_(ROI) taken after receiving the first timestamp and until a second window before receiving from the user a second timestamp marking “no headache”, (iii) label as “headache leaving” TH_(ROI) taken during the second window, and (iv) label as “no headache” TH_(ROI) taken after receiving the second timestamp.

In a third example, the computer may (i) label as “leading to asthma attack” TH_(breath) indicative of the user's breathing pattern (such as thermal measurements of a region on the upper lip) taken during a first window before identifying that the user uses a first inhaler, (ii) label as “first inhaler immediate effect” TH_(breath) taken during a second window after using the first inhaler, (iii) label as “first inhaler long effect” TH_(breath) taken during a third window following the second window, and (iv) label as “second inhaler immediate effect” TH_(breath) taken during a fourth window after identifying that the user uses a second inhaler. Optionally, the computer may use the automated labeling for assessing the user's reaction to using the first inhaler vs using the second inhaler.

In a fourth example, the computer may (i) label as “building concentration” TH_(breath) indicative of the user's breathing pattern and TH_(forehead) indicative of a thermal pattern on the user's forehead taken while the user's software agent indicates that the user does not check distracting websites (such as social networks, news and email) but the user's gaze is not essentially continuously focused on the screen, (ii) label as “concentrated” TH_(breath) and TH_(forehead) taken while the software agent indicates that the user's gaze is continuously focused on the screen and until a certain duration before the user lost concentration, and (iii) label as “start losing concentration” TH_(breath) and TH_(forehead) taken during the certain duration.

In a fifth example, the computer may (i) label as “possibly happy” TH_(ROI) and FSCC taken during a first window before a speech analysis module provides a timestamp that the user is happy, (ii) label as “happy” TH_(ROI) and FSCC taken during a second window after receiving the timestamp, and (iii) label as “angry” TH_(ROI) and FSCC taken during a third window after the speech analysis module provides a timestamp that the user is angry.

In the refinement step, the computer starts guessing the physiological and/or mental states, and asks the user to confirm correct, incorrect, or inapplicable status of the guesses. The refinement step increases fidelity the more it is performed.

In the optional detection step, the computer analyzes in real time feature values generated based on the thermal and/or FSCC measurements in order to alert the user about entering and/or leaving a target state. For example, the computer permits administration of pain medication to the user after the classifier determines that the user experiences pain above a threshold previously determined by the user during the timestamping step. This may reduce addiction by reducing unnecessary administrations of higher dose pain medication. Additionally, the user may be trained to control his/her pain perception during the biofeedback step, which may be more effective after a personalized model has been applied.

In the optional biofeedback step, the computer generates a feedback for the user based on the personalized target state. The biofeedback step may use a standard biofeedback protocol, but instead of training the user towards achieving externally derived thermal and/or FSCC target patterns that suit the wide population, the user is trained to achieve personalized thermal and/or FSCC target patterns that most closely resemble the thermal and/or FSCC patterns found to be predictive during the timestamping and refinement steps.

In one embodiment, the user labels during the timestamping step pairs of undesired and desired states (such as pain vs no pain, migraine vs no migraine, angry vs calmed, stressed vs calmed, concentrated vs not concentrated, sad vs happy, self-focused vs compassionate). Then the biofeedback step trains the user to move out of the undesired state by (i) encouraging changes that bring the current measured thermal and/or FSCC pattern closer to the desired personalized thermal and/or FSCC pattern found to be predictive during the timestamping and refinement steps, and (ii) discouraging changes that bring the current measured thermal and/or FSCC pattern closer to the undesired personalized thermal and/or FSCC pattern found to be predictive during the timestamping and refinement steps.

The following is one example of the information flow in an HMS that includes a head-mounted thermal camera and a computer. In the timestamping step, the head-mounted thermal camera takes thermal measurements, and the user (or computer) adds manual (or automated) timestamps for entering and/or leaving a target state. The timestamping step feeds the machine learning step, in which a machine learning-based training algorithm is used to train a personalized model that is evaluated against user measurements in known states. The machine learning step feeds the refinement step with processed data and questions, and in the refinement step the user answers whether the machine learning algorithm has correctly detected the user's state. Both the machine learning step and the refinement step may provide data to the optional detection and biofeedback steps (which may communicate with each other).

Big data analysis may be performed to identify trends and detect new correlations over users and populations, together with other sources of information, such as other wearable devices (e.g., smart watches, smart shirts, EEG headsets, smart earphones), mobile devices (e.g., smartphone, laptop), and other sources of information (e.g., social networks, search engines, bots, software agents, medical records, IoT devices).

Various embodiments described herein involve an HMS that may be connected, using wires and/or wirelessly, with a device carried by the user and/or a non-wearable device. The HMS may include a battery, a computer, sensors, and a transceiver.

FIG. 57a and FIG. 57b are schematic illustrations of possible embodiments for computers (400, 410) that are able to realize one or more of the embodiments discussed herein that include a “computer”. The computer (400, 410) may be implemented in various ways, such as, but not limited to, a microcontroller, a computer on a chip, a system-on-chip (SoC), a system-on-module (SoM), a processor with its required peripherals, a server computer, a client computer, a personal computer, a cloud computer, a network device, a handheld device (e.g., a smartphone), an head-mounted system (such as smartglasses, an augmented reality system, a virtual reality system, and/or a smart-helmet), a computing device embedded in a wearable device (e.g., a smartwatch or a computer embedded in clothing), a computing device implanted in the human body, and/or any other computer form capable of executing a set of computer instructions. Further, references to a computer or a processor include any collection of one or more computers and/or processors (which may be at different locations) that individually or jointly execute one or more sets of computer instructions. This means that the singular term “computer” is intended to imply one or more computers, which jointly perform the functions attributed to “the computer”. In particular, some functions attributed to the computer may be performed by a computer on a wearable device (e.g., smartglasses) and/or a computer of the user (e.g., smartphone), while other functions may be performed on a remote computer, such as a cloud-based server.

The computer 400 includes one or more of the following components: processor 401, memory 402, computer readable medium 403, user interface 404, communication interface 405, and bus 406. The computer 410 includes one or more of the following components: processor 411, memory 412, and communication interface 413.

Thermal measurements that are forwarded to a processor/computer may include “raw” values that are essentially the same as the values measured by thermal cameras, and/or processed values that are the result of applying some form of preprocessing and/or analysis to the raw values. Examples of methods that may be used to process the raw values include analog signal processing, digital signal processing, and various forms of normalization, noise cancellation, and/or feature extraction.

Functionality of various embodiments may be implemented in hardware, software, firmware, or any combination thereof. If implemented at least in part in software, implementing the functionality may involve a computer program that includes one or more instructions or code stored or transmitted on a computer-readable medium and executed by one or more processors. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another. Computer-readable medium may be any media that can be accessed by one or more computers to retrieve instructions, code, data, and/or data structures for implementation of the described embodiments. A computer program product may include a computer-readable medium. In one example, the computer-readable medium 403 may include one or more of the following: RAM, ROM, EEPROM, optical storage, magnetic storage, biologic storage, flash memory, or any other medium that can store computer readable data.

A computer program (also known as a program, software, software application, script, program code, or code) can be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages. The program can be deployed in any form, including as a standalone program or as a module, component, subroutine, object, or another unit suitable for use in a computing environment. A computer program may correspond to a file in a file system, may be stored in a portion of a file that holds other programs or data, and/or may be stored in one or more files that may be dedicated to the program. A computer program may be deployed to be executed on one or more computers that are located at one or more sites that may be interconnected by a communication network.

Computer-readable medium may include a single medium and/or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store one or more sets of instructions. In various embodiments, a computer program, and/or portions of a computer program, may be stored on a non-transitory computer-readable medium, and may be updated and/or downloaded via a communication network, such as the Internet. Optionally, the computer program may be downloaded from a central repository, such as Apple App Store and/or Google Play. Optionally, the computer program may be downloaded from a repository, such as an open source and/or community run repository (e.g., GitHub).

At least some of the methods described herein are “computer-implemented methods” that are implemented on a computer, such as the computer (400, 410), by executing instructions on the processor (401, 411). Additionally, at least some of these instructions may be stored on a non-transitory computer-readable medium.

Herein, a direction of the optical axis of a VCAM or a CAM that has focusing optics is determined by the focusing optics, while the direction of the optical axis of a CAM without focusing optics (such as a single pixel thermopile) is determined by the angle of maximum responsivity of its sensor. When optics are utilized to take measurements with a CAM, then the term CAM includes the optics (e.g., one or more lenses). In some embodiments, the optics of a CAM may include one or more lenses made of a material suitable for the required wavelength, such as one or more of the following materials: Calcium Fluoride, Gallium Arsenide, Germanium, Potassium Bromide, Sapphire, Silicon, Sodium Chloride, and Zinc Sulfide. In other embodiments, the CAM optics may include one or more diffractive optical elements, and/or or a combination of one or more diffractive optical elements and one or more refractive optical elements.

When CAM includes an optical limiter/field limiter/FOV limiter (such as a thermopile sensor inside a standard TO-39 package with a window, or a thermopile sensor with a polished metal field limiter), then the term CAM may also refer to the optical limiter. Depending on the context, the term CAM may also refer to a readout circuit adjacent to CAM, and/or to the housing that holds CAM.

Herein, references to thermal measurements in the context of calculating values based on thermal measurements, generating feature values based on thermal measurements, or comparison of thermal measurements, relate to the values of the thermal measurements (which are values of temperature or values of temperature changes). Thus, a sentence in the form of “calculating based on TH_(ROI)” may be interpreted as “calculating based on the values of TH_(ROI)”, and a sentence in the form of “comparing TH_(ROI1) and TH_(ROI2)” may be interpreted as “comparing values of TH_(ROI1) and values of TH_(ROI2)”.

Depending on the embodiment, thermal measurements of an ROI (usually denoted TH_(ROI) or using a similar notation) may have various forms, such as time series, measurements taken according to a varying sampling frequency, and/or measurements taken at irregular intervals. In some embodiments, thermal measurements may include various statistics of the temperature measurements (T) and/or the changes to temperature measurements (ΔT), such as minimum, maximum, and/or average values. Thermal measurements may be raw and/or processed values. When a thermal camera has multiple sensing elements (pixels), the thermal measurements may include values corresponding to each of the pixels, and/or include values representing processing of the values of the pixels. The thermal measurements may be normalized, such as normalized with respect to a baseline (which is based on earlier thermal measurements), time of day, day in the month, type of activity being conducted by the user, and/or various environmental parameters (e.g., the environment's temperature, humidity, radiation level, etc.).

As used herein, references to “one embodiment” (and its variations) mean that the feature being referred to may be included in at least one embodiment of the invention. Moreover, separate references to “one embodiment”, “some embodiments”, “another embodiment”, “still another embodiment”, etc., may refer to the same embodiment, may illustrate different aspects of an embodiment, and/or may refer to different embodiments.

Some embodiments may be described using the verb “indicating”, the adjective “indicative”, and/or using variations thereof. Herein, sentences in the form of “X is indicative of Y” mean that X includes information correlated with Y, up to the case where X equals Y. For example, sentences in the form of “thermal measurements indicative of a physiological response” mean that the thermal measurements include information from which it is possible to infer the physiological response. Stating that “X indicates Y” or “X indicating Y” may be interpreted as “X being indicative of Y”. Additionally, sentences in the form of “provide/receive an indication indicating whether X happened” may refer herein to any indication method, including but not limited to: sending/receiving a signal when X happened and not sending/receiving a signal when X did not happen, not sending/receiving a signal when X happened and sending/receiving a signal when X did not happen, and/or sending/receiving a first signal when X happened and sending/receiving a second signal X did not happen.

Herein, “most” of something is defined as above 51% of the something (including 100% of the something). Both a “portion” of something and a “region” of something refer herein to a value between a fraction of the something and 100% of the something. For example, sentences in the form of a “portion of an area” may cover between 0.1% and 100% of the area. As another example, sentences in the form of a “region on the user's forehead” may cover between the smallest area captured by a single pixel (such as 0.1% or 5% of the forehead) and 100% of the forehead. The word “region” refers to an open-ended claim language, and a camera said to capture a specific region on the face may capture just a small part of the specific region, the entire specific region, and/or a portion of the specific region together with additional region(s).

Sentences in the form of “angle greater than 20°” refer to absolute values (which may be +20° or −20° in this example), unless specifically indicated, such as in a phrase having the form of “the optical axis of CAM is 20° above/below the Frankfort horizontal plane” where it is clearly indicated that the CAM is pointed upwards/downwards. The Frankfort horizontal plane is created by two lines from the superior aspects of the right/left external auditory canal to the most inferior point of the right/left orbital rims.

The terms “comprises,” “comprising,” “includes,” “including,” “has,” “having”, or any other variation thereof, indicate an open-ended claim language that does not exclude additional limitations. The “a” or “an” is employed to describe one or more, and the singular also includes the plural unless it is obvious that it is meant otherwise; for example, sentences in the form of “a CAM configured to take thermal measurements of a region (TH_(ROI))” refers to one or more CAMs that take thermal measurements of one or more regions, including one CAM that takes thermal measurements of multiple regions; as another example, “a computer” refers to one or more computers, such as a combination of a wearable computer that operates together with a cloud computer.

The phrase “based on” is intended to mean “based, at least in part, on”. Additionally, stating that a value is calculated “based on X” and following that, in a certain embodiment, that the value is calculated “also based on Y”, means that in the certain embodiment, the value is calculated based on X and Y.

The terms “first”, “second” and so forth are to be interpreted merely as ordinal designations, and shall not be limited in themselves. A predetermined value is a fixed value and/or a value determined any time before performing a calculation that compares a certain value with the predetermined value. A value is also considered to be a predetermined value when the logic, used to determine whether a threshold that utilizes the value is reached, is known before start performing computations to determine whether the threshold is reached.

The embodiments of the invention may include any variety of combinations and/or integrations of the features of the embodiments described herein. Although some embodiments may depict serial operations, the embodiments may perform certain operations in parallel and/or in different orders from those depicted. Moreover, the use of repeated reference numerals and/or letters in the text and/or drawings is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. The embodiments are not limited in their applications to the order of steps of the methods, or to details of implementation of the devices, set in the description, drawings, or examples. Moreover, individual blocks illustrated in the figures may be functional in nature and therefore may not necessarily correspond to discrete hardware elements.

Certain features of the embodiments, which may have been, for clarity, described in the context of separate embodiments, may also be provided in various combinations in a single embodiment. Conversely, various features of the embodiments, which may have been, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. Embodiments described in conjunction with specific examples are presented by way of example, and not limitation. Moreover, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the embodiments. Accordingly, this disclosure is intended to embrace all such alternatives, modifications, and variations that fall within the spirit and scope of the appended claims and their equivalents. 

1. A system comprising: a head-mounted contact photoplethysmography device configured to measure a signal indicative of photoplethysmogram signal at a first region comprising skin on a user's head (PPG signal); a camera configured to capture images of a second region comprising exposed skin on the user's head; wherein the camera is located more than 10 mm away from the user's head; and a computer configured to detect a physiological response based on: (i) imaging photoplethysmogram signals (iPPG signals) recognizable in the images, and (ii) correlations between the PPG signal and the iPPG signals.
 2. The system of claim 1, wherein the camera is an inward-facing head-mounted camera, and both the camera and the head-mounted contact photoplethysmography device are physically coupled to smartglasses or to a smart-helmet, which is designed to measure the user in day-to-day activities, over a duration of weeks, months, and/or years.
 3. The system of claim 1, wherein the camera is integrated in a non-wearable device, and the computer is further configured to authenticate that the user is using the non-wearable device by checking whether correlations between the PPG signal and the iPPG signals reach a predetermined threshold.
 4. The system of claim 1, wherein the computer is further configured to extract the iPPG signals from the images based on values of time-segments in which the iPPG signals were expected to appear as a function of locations of respective regions of the iPPG signals relative to location of the contact PPG device.
 5. The system of claim 1, wherein the computer is further configured to extract from the PPG signal at least one of the following parameters: systolic peak, dicrotic notch, diastolic peak, interbeat interval, and systolic-diastolic peak-to-peak time; and the computer is further configured to utilize at least one of the parameters to correlate between the PPG signal and the iPPG signals.
 6. The system of claim 1, wherein the computer is further configured to extract from the PPG signal times corresponding to at least one of the following types of fiducial points: systolic peaks, dicrotic notches, and diastolic peaks; and the computer is further configured to utilize the times to extract corresponding fiducial points in the iPPG signals by adding to the times an offset in order to determine when the corresponding fiducial points manifest in the iPPG signals.
 7. The system of claim 6, wherein the offset is proportional to at least one of the following values: a heart rate of the user, and a blood pressure value of the user.
 8. The system of claim 1, wherein the iPPG signals comprise multiple values for different sub-regions of the second region, and the physiological response is detected based on differences between amplitudes of the values recognizable in the different sub-regions of the second region.
 9. The system of claim 8, wherein the physiological response is indicative of an allergic reaction, and the sub-regions of the second region comprise portions of at least two of the following areas on the user's face: nose, upper lip, lips, cheeks, temples, periorbital area around the eyes, and the forehead.
 10. The system of claim 8, wherein the physiological response is indicative of a stroke, and the sub-regions of the second region comprise at least one of the following pairs on the user's face: left and right cheeks, left and right temples, left and right sides of the forehead, and left and right sides of the periorbital area around the eyes.
 11. The system of claim 8, wherein the physiological response is indicative of a migraine, and the sub-regions of the second region comprise at least one of the following pairs on the user's face: left and right sides of the forehead, left and right temples, left and right sides of the periorbital area around the eyes, and left and right cheeks.
 12. The system of claim 8, wherein the physiological response is indicative of a blood pressure value that is calculated based on differences in pulse transit times detectable in the sub-regions of the second region; wherein the sub-regions comprise at least two of the following areas on the user's face: left temple, right temple, left side of the forehead, right side of the forehead, left check, right cheek, nose, periorbital area around the left eye, and periorbital area around the right eye.
 13. The system of claim 8, wherein the physiological response is indicative of at least one of stress, emotional response, and pain, which are calculated based on changes to hemoglobin concentrations observable in the iPPG signals relative to previous measurements of hemoglobin concentrations observable in the iPPG signals of the user; wherein the sub-regions comprise at least two of the following areas on the user's face: lips, upper lip, chin, left temple, right temple, left side of the forehead, right side of the forehead, left check, right cheek, left ear lobe, right ear lobe, nose, periorbital area around the left eye, and periorbital area around the right eye.
 14. The system of claim 8, wherein the camera comprises two or more inward-facing head-mounted cameras, and the second region comprises two or more regions on the user's head that are respectively captured by the two or more inward-facing head-mounted cameras.
 15. The system of claim 1, wherein the computer is further configured to refrain from detecting the physiological response when a different between a first heart rate determine based on the PPG signal and a second heart rate determine based on the iPPG signals is greater than 5 beats per minute.
 16. The system of claim 1, further comprising a head-mounted sensor configured to measure a signal indicative of timing of the user's inhalation phase and/or exhalation phase (respiratory-phase signal); wherein the computer is further configured to detect the physiological response also based on correlations between timings of the iPPG signals and the respiratory-phase signal.
 17. A method comprising: measuring a signal indicative of a photoplethysmogram signal at a first region comprising skin on a user's head (PPG signal) utilizing a head-mounted contact photoplethysmography device; capturing images of a second region comprising exposed skin on the user's head utilizing a camera; wherein the camera is located more than 10 mm away from the user's head; and detecting a physiological response based on: (i) imaging photoplethysmogram signals (iPPG signals) recognizable in the images, and (ii) correlations between the PPG signal and the iPPG signals.
 18. The method of claim 17, wherein the physiological response is indicative of a value of blood pressure, and is calculated based on differences in pulse transit times detectable in portions of the images that include sub-regions of the second region; and wherein the sub-regions comprise at least two of the following areas on the user's face: left temple, right temple, left side of the forehead, right side of the forehead, left check, right cheek, nose, periorbital area around the left eye, and periorbital area around the right eye.
 19. The method of claim 17, wherein the physiological response is indicative of at least one of stress, an emotional response, and pain, which are calculated based on changes to hemoglobin concentrations observable in the iPPG signals relative to previous measurements of hemoglobin concentrations observable in the iPPG signals of the user; wherein the sub-regions comprise at least two of the following areas on the user's face: lips, upper lip, chin, left temple, right temple, left side of the forehead, right side of the forehead, left check, right cheek, left ear lobe, right ear lobe, nose, periorbital area around the left eye, and periorbital area around the right eye.
 20. A head-mounted imaging photoplethysmography system, comprising: a head-mounted contact photoplethysmography device configured to measure a signal indicative of a photoplethysmogram signal at a first region comprising skin on a user's head (PPG signal); a head-mounted camera configured to capture images of a second region comprising exposed skin on the user's head; wherein the camera is located more than 10 mm away from the user's head; and a head-mounted computer configured to: identify times at which fiducial points appear in the PPG signal; calculate, based on the times, time-segments in which the fiducial points are expected to appear in imaging photoplethysmogram signals recognizable the images (iPPG signals); and detect a physiological response based on values of the iPPG signals during the time-segments. 